AdWords – Google’s primary advertising distribution network encompassing Pay-Per-Click (PPC) , text and banner advertising on web sites.

AdSense – A Google advertising program where website owners can opt to include advertising on their site and share a portion of the click through revenue.

B to B or B2B, Business to Business - Internet-based business-to-business commerce typically engaged in by manufacturers, wholesalers and suppliers who market to other businesses.

B to C or B2C, Business to Consumer or Business to Customer - Retailers who typically market to an individual consumer rather than a business.

Click Through or Click Through Rate - A measure of the number of times a user clicks on a link to take a further action. The number of times users click on an advertisement or link in an email, or on a search engine results page to visit a site. For a banner that was clicked 100 times and displayed 1000 times, the CTR is 100:1000 or 1:10. This can be changed to a percentage value by multiplying by 100: 1/10 * 100 = 10%, meaning 10% of the impressions have led to clicks on the banner.

Click Tracking - The use of pieces of code to track the click through activity of inbound and outbound links on a website or in an email.

CPGs, Consumer Packaged Goods - Any consumable goods that are ready for purchase by a consumer.

CPC, Cost Per Click - The amount an advertiser pays each time an ad is clicked. Sometimes this is set through a bidding process, other times the cost is determined by calculating the CPI/%CTR.

Conversion Rate – The measure of how many visitors to your site make a purchase as compared to the total number of all visitors to your site. Calculated by dividing total number of visitors by number of visitors who make a purchase.

CPA, Cost Per Action, or Cost Per Acquisition - In the PPA advertising model, the CPA is the actual cost paid when the action is completed.

CPI, Cost Per Impression - This is the cost paid each time an online advertisement, such as a banner ad, is displayed.

CPL, Cost Per Lead - A payment arrangement where an advertiser pays a publisher for a lead, which is a verified potential customer. For example, the publisher may run an ad for a free trial. A user that clicks on the free trial link is a lead that may become a future customer, and the publisher is paid a certain CPL.

CPM, Cost Per Thousand Impressions - Literally, “cost per mille,” which in Latin means thousand. Sometimes, CPI and CPM are used interchangeably, as when an ad campaign is sold on the basis of 1000 impressions. One thousand impressions at a $10 CPI results in a $10,000 CPM ad campaign.

CPS, Cost Per Sale - The cost an advertiser pays only for those click-throughs on an ad that result in a purchase.

CPT, Cost Per Transaction - Similar to CPA, in that advertisers pay whenever a visitor who clicked on their advertisement completes a transaction.

Directory - Searchable guide of web sites often organized by subject and compiled and reviewed by human editors. The value of directories are sometimes in question, but it is still desirable to have a site listed in some, for example, the leading Open Directory Project (DMOZ), to provide another way for people to find a site.

Dynamic Content or Dynamic Web Page - Information on web pages that changes automatically, in response to different contexts or conditions. The content may be text, images, form fields, etc.

EPC, Earnings Per Click - The commission you pay to a publisher or affiliate advertiser for each click (visitor) they send to you. If you pay $20 after receiving 100 visitors, $20/100 = 0.20 and the EPC is 20 cents per click.

eCPM, Effective Cost Per Mille - Measures what a publisher would receive if their advertising inventory was sold on a CPM basis as opposed to a CPA, CPC, or CPT basis.

Entry Page - Any page by which a visitor enters your website.

Exit Page - Any page where a visitor leaves your website.

Google Bot - The name given to the crawlers that index pages into the Google index, or master web site directory which Google uses to display its results.

IP Address - A unique number which identifies a computer or system.

Keyword - A word or phrase that is used as a search term in a search engine. Optimizing a site involves researching the keywords or phrases that users enter in order to find web sites, and then including those terms in the content of the site where appropriate.

Keyword Density – The repeated use of keywords or search terms in an optimized page as compared to the content not containing the keyword or phrase. Search engines consider keyword density in determining the relevance of a particular page to the search query in question, although there is no consensus on what number an optimum keyword density should be.

Keyword Frequency – A measure of how often a keyword appears in optimized content. Keyword frequency is but one factor to consider in looking at how well an optimized page will rank in search engine results pages. Repeating a keyword too often in a page can be considered a spammy, deceptive practice and may result in a penalty.

Keyword Research – A first step in website optimization, keyword research looks at the particular words and phrases user enter to search for products and services online. Knowing the right keywords to use allows the content writer to compose content that includes the phrases.

Keyword Stuffing – The act of including an overabundance of repetitions of a keyword or phrase in a website. This is generally a deceptive practice aimed at artificially inflating a site’s relevance to search engines.

Link Farm - A group of websites that are interlinked to each other. Link farming is a form of spamming due to manipulation of the importance search engines place on linking. It is far better to put effort into natural, relevant, high quality links than to buy or exchange links with link farms.

Link Popularity – Incoming links to a site are considered a vote of confidence or popularity for a website, and many search engines use a site’s link profile as a factor in their ranking system. The importance of each incoming link is weighed based on the authority of the other sites, and if the content of the other site is related to the content of the site it is linking to.

MLM, Multi-level Marketing - Often indistinguishable from “pyramid schemes” in which commissions are paid to each seller based on the number of additional sellers that they can recruit.

Open Directory Project or DMOZ – The leading online directory of web sites. Volunteer editors compile and maintain the database, and make it available to search engines as a way of providing relevant results to search engine queries.

PPA, Pay Per Action - Advertisers pay only when pre-specified actions are completed by a user on their site, such as when a user makes a purchase, signs up for a newsletter, fills out a form, or downloads a free trial.

Pay Per Click - An advertising model where advertisers pay only when a user clicks on an ad to visit the advertiser’s website.

P to P or P2P, Peer To Peer - Not really a marketing acronym but it is fairly common; P2P refers to file sharing over the Internet or on small networks.

Pop Under – An advertisement that loads under a page so that it is only visible when the current page is closed.

Pop-Up – A window, usually displaying an advertisement, that opens on top of or above the current window.

Relevance - A subjective measure of how well a web site matches with the intentions of the user who searched for the information. Search engine algorithms place great importance on relevance, and weigh a site’s relevance to the search at hand in order to place the most relevant sites higher up in the serps.

Search Engine - A search engine is an online database of resources and information contained on the Internet. The search engine indexes (catalogs) web pages and documents, stores the results, and makes them available when users search based on the factors in the algorithm. The top three major search engines are Google, Yahoo!, and Ask.com (formerly MSN).

Search Engine Marketing (SEM) – An umbrella term which includes on-page search engine optimization practices, and online marketing methods of driving traffic to a site. SEM includes achieving higher rankings in results through optimization as well as paid advertising campaigns.

Search Engine Optimization (SEO) - Changes made to the content and code of a web site with the goal of increasing it's rankings in search engine results pages and directories. Changes may include rewriting the site’s written content, adding or altering page titles or Meta tags, analyzing the site’s technical structure, and building incoming links from other quality sites.

Search Engine Placement – A site’s position in the search engine results pages, as well as the efforts made to improve that placement, similar to optimization.

Search Term - A word or phrase used entered into a search engine search bar in order for a user to receive information about that word or phrase from web sites.

SERP or search engine results page - The list of search results that are returned by a search engine in response to a search query, with the most relevant results placing higher on the page.

Spamming – An umbrella term for any deceptive practice which is designed to mislead consumers for commercial purposes, or artificially inflate a site’s rankings in the search engine results pages. Examples of spam or spamming include keyword stuffing, hidden text, or the practice of sending unsolicited bulk email. Most search engines will penalize a site they find to be engaging in spam techniques.

Spider or ‘bot’ - An automated program that follows links to visit web sites to index or catalog them for a search engine or directory. The contents of the web pages are then stored in a searchable database.

Stemming – Word variations which some search engines consider in determining which search results to display. For example, a search engine that uses stemming might consider the search term “snow” and return results including “snow,” “snows,” and “snowing.” Stemming can have an impact on the selection of keywords for an optimization campaign.

Stop Word – Stop words are common words that are ignored by a search engine in returning the results of a query, including such general words as ‘the,’ ‘a,’ ‘of,’ ‘my,’ etc.

Unique Visitor - A real person who has visited a web site as opposed to a spider or bot. Unique visitors are identified by their IP address.

URL or Universal Resource Locator - An address specifies the location of an Internet web site, page or document.