Here is a definition of a blog according to Wikipedia.com:

A weblog, which is usually shortened to blog, is a website where regular entries are made (such as in a journal or diary) and presented in reverse chronological order. Blogs often offer commentary or news on a particular subject, such as food, politics, or local news; some function as more personal online diaries. A typical blog combines text, images, and links to other blogs, web pages, and other media related to its topic. Most blogs are primarily textual although many focus on photographs, videos or audio. The word blog can also be used as a verb, meaning adding an entry to a blog.
The difference between a blog and a traditional website is the way in which they are updated. Websites are typically static content, updated only periodically, where as blog technology allows a user to update the content as often, or as quickly as they like. Originally blogs were used by individuals as publicly available online journals. In the past few years, businesses and politicians have started to discover the power of the blog, and their popularity and use has taken off.

One way blogs and webites differ is in the way that search engines view them. Because of the static nature of a website search engines visit them relatively in-frequently making it difficult for a site to get noticed and listed in search results. Blogs on the other had are visited often by search engine spiders due to their dynamic content nature of posts. It's much easier to get a blog ranked high in the search engines compared to websites.

It's very easy to set up a blog. You can set up a blog in less then five minutes. The nice thing about a blog is that it's like having your own website but you don't have to learn how to make a website or pay someone to host it.

If you want to see how easy it is to set up a blog you can set one up for free at Wordpress.com or Blogger.com.

Once you set up a blog you can add ?posts? to your blog every hour, day, week or month. You can add pictures to your blog and let other people post to your blog.

So basically a blog is like a website but easier to create and manage. The simplicity of blogging has made it one of the fastest growing trends on the internet. Even my offline father can go to blogger and set up a blog about our family

Now that we all know what a blog is let's talk about how blogs can make you money

Below is a list of some of the ways blogs can make you money:

Googles Adsense can be put on blogs.
Banners promoting products can be put on blogs.
Affiliate Links can be placed in blog Entries.

Successful Profit making blogs take advantage of the above listed items.

Since anyone can start a blog and it's free to run a blog, the art of blogging has become one of the easiest and cheapest ways to make money on the Internet.