What is a Blog?
One of the things that is so amazing about blogs is their
simplicity.
Think about a "normal Web site." It usually has a home page, with
links to lots of sub-pages that have more detail. HowStuffWorks is
like this, with thousands of information pages all organized under
a home page. A small business site follows the same format -- it
might have a home page and five or 10 sub-pages. Most traditional
Web sites follow this format. If the site is small, it is sort of
like an online brochure. If it is large, it is like an electronic
encyclopedia.

A typical Web site has a home page that links to sub-pages within
the site. CNN.com, pictured above, is typical of this genre. The
CNN site contains thousands of articles all organized into big
categories. The categories and all the latest stories are accessed
from the home page.
A blog is much simpler:
* A blog is normally a single page of entries. There may be
archives of older entries, but the "main page" of a blog is all
anyone really cares about.
* A blog is organized in reverse-chronological order, from most
recent entry to least recent.
* A blog is normally public -- the whole world can see it.
* The entries in a blog usually come from a single author.
* The entries in a blog are usually stream-of-consciousness. There
is no particular order to them. For example, if I see a good link,
I can throw it in my blog. The tools that most bloggers use make it
incredibly easy to add entries to a blog any time they feel like
it.

A typical blog has a main page and nothing else. On the main page,
there is a set of entries. Each entry is a little text blurb that
may contain embedded links out to other sites, news stories, etc.
When the author adds a new entry, it goes at the top, pushing all
the older entries down. This blog also has a right sidebar that
contains additional permanent links to other sites and stories. The
author might update the sidebar weekly or monthly.
Basically, a blog is a lot like an online journal or diary. The
author can talk about anything and everything. Many blogs are full
of interesting links that the author has found. Blogs often contain
stories or little snippets of information that are interesting to
the author.
Why Blog?
Even though blogs can be completely free-form, many blogs have a
focus. For example, if a blogger is interested in technology, the
blogger might go to the Consumer Electronics Show and post entries
of the things he/she sees there. If a blogger is interested in a
certain disease, he/she might post every news article and every
piece of research he/she finds on the disease. If a blogger is
interested in economic issues, he/she might post links to articles
that discuss the economy and then offer commentary on them.
There are people who use their blogs simply as a scrapbook -- a
form of online memory. Whenever the author finds a link or a
snippet of information that he/she wants to remember, it gets
posted in the blog. Even if no one else ever looks at it, it is
still useful to the author because the blog is a searchable
electronic medium that the author can access with a Web browser
anywhere in the world.
In other words, a blog can be anything the author wants it to be.
The thing that all blogs have in common is the
reverse-chronological ordering of entries.