Blogging allows would-be Web masters to create content without the overhead of creating a new site, applying for a Web Domain name, designing and finally writing it. There are many great sites that allow you to create content almost immediately that can start to attract traffic right away. Blogger.com is one such site; WordPress is another. Both of these allow you to easily adjust the look and feel of your site, and they provide you with a domain name that you can use right away. Alternatively, you can use their software to post to your own domain if you prefer to do so.
Blogger.com allows you to use AdSense and affiliate links in your posts, where WordPress does not (but you can if you use your own domain).
When blogging it makes the most sense to stick to one single subject per blog. If you have more than one topic you want to write on, then create a new blog with its own domain for each topic. This helps keep the search engines happy, and your domain ranked high.
In fact, there is even more benefit to having multiple blog domains, especially if they are similar but distinct topics. By having links to each of your other domains in every blog, you improve the search engines' estimation of the importance of your site because of incoming links. The fact that they all originate from the same writer does not matter to the search engines. Each blog site will get a boost in the search rankings, which should result in increased traffic.
If you are not familiar with the history of blogging, it originated as a method of keeping and publishing a diary. The term "blog" is simply a shortened form of "Web log", and there have been some famous and infamous blogs in the early days. However, the days of keeping a diary and expecting to get a loyal following are pretty much at an end. If that's what you want to do, then that's fine; just don't expect much from it.
The other factor that adds to the benefits of blogging is that most blogging sites and software allow for visitor feedback. Not only does this increase your interaction with your visitors, but it actually creates new content that search engines can list. More than once I have had new visitors come to a blog site when their search came up with a link to a comment left by a visitor.
As with content driven Web sites, there are many ways to monetize your blog. First and most obvious is to use Google AdSense; another is to post affiliate links. For more information on these, see my previous blog on Content Driven Sites.
So, since you are already on this site, why don't you start your blog right now! But before you do, leave me a nice, long comment with lots of searchable terms in it!