Google is the major search engine in IT field. It searches with amazing speed and very relevant results. There is a product of google is "Google Adsense". This is useful for owners of websites (usually named as Publishers in google adsense) and every person who is having blog.

https://www.google.com/adsense

Yoou have to join a account to create the adsense account. This is very good opportuinity to earn the money online with a little effort. After sign the account you need to wait for acceptance of account. whenever after 2-3 days your account will be accepted you may have rights to generate the advertisement blocks for your website according to your need. Then you have to place only that code in your website. After that you need to attract the web traffic for your website/blog. When ever any person will click on advertisement block of your website then you will be credited with some amount.

But remember that if google find the fraud or multiple amount of clicks from a machine then you may loose this online business with google. So dont try to click on advertisement.