If you have been online for quiet some time you might have noticed those tiny ads on many websites with the little "ads by google" notice beneath them.
These ads are called "Adsense", they are paid advertisements and can be a very lucrative income source for the person posting them on his/her website.
Whenever someone visits your website Google displays these ads wich are very targetted to your websites content. This is what its all about, since people come to your website with a specific interest Google will display ads reflecting that topic.
That means that any ad that is displayed fits the interest of the person viewing it. Since Google pays you for each clicktrough this can be very lucrative if done right. Here are just a couple of examples on how you can get the most from Adsense.
Focussing on one specific topic helps increase your clicktroughs because the ads Google displays will be extremely targetted to the topic the person is allready viewing.
For example you could make a website purely on growing flowers. People who visit your website are already interested in gardening and Google will likewise display ads on that topic.
A great tool to check wich keywords might be shown by Google on your website is http://www.about-adsense.com/adsense-web-tool.html
The more targeted Google's ads are the more clicktroughs you will get and the more you will earn.
Search for the keywords that have the highest bids and optimize your website to them.
When you setup an account at http://www.adwords.com you can use Googles keyword tool to view wich keywords pull the most visitors and how much the advertisers are paying for each click. Some keywords are as much as $100 a click think of what you earn when you optimize your website to them.
Next you optimize your sites content to these keywords, you can do this by either creating content yourself or by using other peoples content like for example articles from third parties wich you can find at for example http://www.ezinearticles.com.
Remember its all about targeted content, the more targeted your content is the more target Google's ads will be and the more clicks you will generate.
Have fun!