If you're just geatting started, there's a simple formula for you to understand how to earn money with google adsense:
Revenue = Traffic * CTR * CPC
You probably understand what traffic means.
So CTR is Click Through rate
, and it means how many of your visitors are clicking ads. It actually depends on how your site is adsense-optimized.
CPC is Cost Per Click. Different words have different costs. Some can be about $0,01, some are over $10.