What is Adsense

Google.com earns most of its revenue by allowing other website owners to advertise on their result pages.
This is managed through a program they call Adwords.

You can earn a share of the revenue that Google earns from AdWords by displaying these same text ads on your site.This program is called AdSense.

Every website owner should join the program. Even if your site is just for information purposes, you can still participate and make decent money with AdSense. So if you are one of those people who wants to make money on-line, this is an excellent way to start.