A blog (a contraction of the term "web log") is a type of website, usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in reverse-chronological order. "Blog" can also be used as a verb, meaning to maintain or add content to a blog. -- Wikipedia
Even if you're fairly new to the online world, you've probably started hearing this funny-sounding word thrown about. "Blog" is just a shortening of "Web Log", and generally refers to an online journal or diary. Technically speaking, any website which is updated frequently could fall under this definition, but blogs generally have several specific features which distinguish them from other websites: First, they're usually updated fairly regularly with stories, articles, essays & ideas of the day by the owner(s) of the website; second, they're generally interactive, featuring the ability for visitors to provide feedback comments which appear directly on the blog site for other visitors to also read and respond to (similar to a Message Board). Finally, blogs usually have a more casual atmosphere than the typical corporate/business website, and generally reflect the personalities or personal viewpoints of the owner(s).
From a technical standpoint, a blog is really just a type of content management system (see above), as it provides the means for both the website owner(s) as well as website visitors to add, delete or edit content (usually text, but sometimes photos or other content as well) directly through the web interface, without having to know or learn a lot of HTML coding or file upload programs.
There are numerous open-source blogging tools available on the web; Brainwrap can help you find the right blogging solution to get you started!