Blogs - an abbreviation of 'weblogs' -  web sites which contain dated entries in reverse chronological order (most recent first) about a particular topic. Functioning as an online newsletter, blogs can be written by one person or a group of contributors. Entries contain commentary and links to other Web sites, and images as well as a search facility may also be included. A blog with video clip entries instead of text is a "video Weblog" .

The term "weblog" was coined by Jorn Barger on 17 December 1997. The short form, "blog," was coined by Peter Merholz. He broke the word weblog into the phrase "we blog" in the sidebar of his weblog in April or May of 1999. "Blog" was accepted as a noun (weblog shortened) and as a verb ("to blog," meaning "to edit one's weblog or to post to one's weblog").
Justin Hall, who began eleven years of personal "blogging" in 1994 while a student at Swarthmore College, is generally recognized as one of the earliest bloggers. After a slow start, blogging rapidly gained in popularity: the site Xanga, launched in 1996, had only 100 diaries by 1997, and over 50 000 000 as of December 2005.

The definition of blogs is constantly evolving as blogs move into the mainstream, shedding their image as the bastion of the self-obsessed who just have to self-express. Thousands of new blogs are being created every day, for all sorts of purposes. Rather than existing to catalog someone's personal life, many blogs serve as discussion communities about particular issues.

Nor does a blog have to have one author. Some of the most interesting blogs have multiple regular contributors. And some large corporations are using blogs internally as communications channels.

Blog usage spread incredibly due to the "tool" which is known as RSS. RSS stands for Rich Site Summary or Real Simple Syndication. Either way, RSS is a real important technology that information specialists and educators would be well advised to harness sooner rather than later. In simple terms, Weblogs (and an ever-growing number of other sites) generate a behind-the-scenes code in a language similar to HTML called XML. This code, usually referred to as a "feed" (as in "news feed"), makes it possible for readers to "subscribe" to the content that is created on a particular Weblog so they no longer have to visit the blog itself to get it. As is true with traditional syndication, the content comes to you instead of you going to it.

There  is a real-time search engine - Technorati - that keeps track of what is going on in the blogosphere — the world of weblogs.Technorati displays what's important in the blogosphere — which bloggers are commanding attention, what ideas are rising in prominence, and the speed at which these conversations are taking place. Technorati makes it possible for you to find out what people on the Internet are saying about you, your company, your products, your competitors, your politics, or other areas of interest — all in real-time. All this activity is monitored and indexed within minutes of posting. Technorati provides a live view of the global conversation of the web.