Google adsense program is an advertisements program that works on CPC and CPM ads. if you have a blog or website just go to google adsense fill out there form and apply for an account they will ask all the details about you and ur blog/website. then they will see if your blog/website is up to there standards and if so they send you an email tell you that you have been accepted. then you can go to ur adsense account and start putting up advertisement on your sit/blog. CPC ads work on the basis of how many clicks you get on the ad. CPM work on the per 100 impressions rule, you mostly earn $1 for 100 impressions on the ad but it can vary.