The barebones definition of a forum is the ability for people to start threads and reply to other people's threads. However, most forum software provides considerably more than this.
Most forum software allows more than one forum to be created. These forums are containers for threads started by the community. Depending on the permissions of community members as defined by the board's administrator, they can post replies to existing threads and start new threads as they wish.
Forum software can be broadly divided between those which allow visitors to post anonymously, and those which attribute posts to a registered username.
For username-based software, visitors register using a username and a password for validation purposes. In these types of forums, the members are often able to customise both how their posts display to others and how the board appears to them. Username-based software may provide for anonymity by allowing visitors to post without registration.
Anonymous forums may offer full anonymit, but no registration. In order to provide the same set of features as registration-based forums, anonymous forums especially in Asia use a system of tripcodes, derived by encrypting a plaintext password put in the name field. Although blog comment pages are not Internet forums, they often use the anonymous system for the sake of simplicity.
Backlinks are incoming links to a website or log. The number of backlinks is an indication of the popularity or importance of that website.
Search engines often use the number of backlinks that a website has as one of the factors for determining that website's search engine ranking. For example, Google uses backlinks to help determine a site's rank. To see a site's PageRank, you need to use the Google Toolbar, view the bar graph indicating a website's PageRank in Google's directory, or download the PageRank plugin for Mozilla Firefox.
You can determine the approximate number of backlinks a website has when doing a search at Google by adding "link:" before the website's URL.
