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Blog (a blend of the term web log) is a type of website or part of a website.
Blogs are 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.
A blog is a website where entries are written in chronological order and commonly displayed in reverse chronological order.
source : http://en.wikipedia.org/wiki/Blog
A blog is your best bet for a voice among the online crowd.
It's a personal website, packed with features, as easy to use as your e-mail.
A BLOG is usually updated frequently, maybe monthly, weekly or even daily, it all depends on the blogger.
Most blogs enable the visitors to post comments and/or suggestions allowing interactivity between the blogger and the visitors.
Source : http://www.helpwithpcs.com/jargon/blog.htm