A blog (a contraction of the term "Web log") is a Web site, 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.
How to write a blog post
Do it like this: Joel on Software.
An appropriate illustration,
A useful topic, easily broadened to be useful to a large number of readers,
Simple language with no useless jargon,
Not too long,
Focusing on something that people have previously taken for granted,
That initially creates emotional resistance,
Then causes a light bulb go go off
Causes the reader to look at the world differently all day long.