A-List: Supposedly a list of bloggers (also called A-Listers) that receives more traffic and attention than the rest of the blogosphere. The existence of such an A-List is debated, as well as the reasons behind the higher popularity of those bloggers.

AdSense: The most popular advertising network on the Internet. It is owned by Google, and it allows bloggers to monetize their blogs by displaying contextual text messages. Every time someone clicks on one of the text links, the blogger will earn some money (ranging from $0.01 up to $50 in some rare cases).

AdWords: The opposite end of AdSense. Google AdWords enables companies and individuals to promote their products, services and websites under a cost per click (CPC) model. The advertiser needs to specify the keywords that he wants to target, and how much he is willing to pay for each click. The ads might appear on Google’s search results as well as on the AdSense units found on other websites (called “Content Network).

Affiliate Marketing: A popular way to make money online where you have a merchant that is willing to let other people (affiliates) sell his own products or services, in exchange for a commission. Commissions can be fixed or variable, and based on clicks, leads or sales.

Akismet: The most popular spam filter plugin for WordPress blogs. It was created by the same company that coded WordPress, called Automattic.

Alexa: An internet company (subsidiary of Amazon.com) that tracks the traffic for all websites on the Internet. The rankings used to be inferred from the statistical usage of a browser toolbar. Recently they changed the algorithm to remove the toolbar bias in favor of technology related website. Keep in mind that the lower the Alexa ranking, the higher the traffic of the website. There is some controversy regarding the accuracy of the rankings.

Anchor Text: The text of a backlink. Most search engine experts agree that the archor text is a factor that can influence largely the search rankings of a website or web page. The more topical they are the better (provided some variety is included, else a spam penalty could occur).

Archives: A section of a blog where all or some of the existing posts are displayed. They can be displayed by category, by month, by year and so on.

Atom: A web feed syndication format, developed as an alternative for RSS. It basically enables people to receive updates from a website whenever new content is published.

Automattic: Company founded by Matt Mullenweg, and responsible for the development of WordPress.org (the blogging software) and WordPress.com (the hosting platform), among other projects.

Backlinks: Hyperlinks present in other blogs or websites that point either to the homepage or to internal pages of a website. They are important because Google and other search engines relate the number and quality of backlinks to the trust level of that website.

Blackhat: A group of SEO and online marketing techniques that are not necessarily ethical, and sometimes not even legal. Hiding text behind images or using doorway pages with redirects are examples of blackhat techniques.

Blog: A specific type of website where the author publishes his thoughts, ideas or knowledge about different topics. Usually the content is published in small articles, called posts, and in chronological order. Blogs emerged as online diaries, but today they cover all niches, and compete head to head with mainstream media.

Blog Carnival: An event where bloggers get together to create a collection of articles covering a common topic. Most of the times they have one hosting blog, and participant blogs that will send their contributions to the carnival.

Blogger: Anyone who owns or authors a blog. Blogger is also the commercial name of Google’s hosted and free blogging platform (recognized by the .blogspot extension).

Blogging: The act of writing something on a blog. It can also mean the broader range of activities that bloggers perform (e.g., interacting with visitors, researching content and so on).

Bloglines: One of the most popular RSS feed readers. It is a web-based application that allows the user to subscribe to and manage RSS feeds.

Blogosphere: Term used to describe the universe created by all blogs, its connections, networks and conversations.

Blogroll: A once very popular feature on blogs that allowed the author to share with his readers a list of recommended external blogs. This section was usually included on the sidebar of the blog. These days fewer and fewer bloggers are still using a blogroll.