What is the definition of...

Affiliate (a.k.a Associate for Amazon.com's program)
- usually a partner who resells for another person and gets paid per CPA.

Alternate Text (ALT TXT)
- text associated with a specific webpage image that gets displayed when the Internet user hovers the mouse over the image. Alt tags should convey what the image/website is about and contain relevant keywords because they are spidered by search engines.

Anchor Text
- the actual text part of a textlink and greatly affects your rankings in search results.

Backlink (a.k.a Incoming Link or Inbound Link)
- links that point to your website from other/external websites. Backlinks can be in the form of text (textlink), image or flash file. Depending on the topic, PageRank (PR) and number of outbound links on that webpage, backlinks affect your ranking on SERPs.

Click Through Rate (CTR)
- ratio of the number of clicks on an advertisement against the number of page views, e.g. 6% CTR means for every 100 people who look at the advertisement, 6 will click on it.

Cloaking
- serving different content to search engine spiders and to human visitors, e.g. the web server feeds spiders keyword-rich content, thus fooling the search engine into placing that page higher in the search results. Yet when the visitor clicks on the link they are given totally unrelated content. This practice is known as "blackhat SEO" and get your website banned if caught.

Contextual Ad
- advertisements that are dynamically displayed based on the page content, e.g. Dell Inspiron laptop advertisements on a laptop blog.

CPA (Cost per Action)
- cost paid to a publisher when a visitor from his/her website completes a set of agreed action, e.g. completing a survey and downloading trial software.

CPC (Cost per Click)
- cost paid to a publisher when a visitor from his/her website clicks on your advertisement.

CPM (Cost per Thousand)
- cost paid to a publisher for every 1,000 times your advertisement is shown on his/her website.