Explain google adsense?

Without Google Adwords there won't be Google Adsense.

Google Adsense is for publisher & Google Adwords is for Advertisers.

There are estimated about 50K unique search a day on Google search engine. So there are millions of people use Google search engine freely to find any type of information they want. Google serve them the most relevant content, And you know what, not a single cents were charge by Google.

So where does Google generate a revenue billions every year?

It's Advertising - Google Adwords. (you will see the ads on the right side of Google SERP)

Google offer any advertisers to use Google Adwords service to target any keyword search by visitors. They charge it per click.

That is why they call it pay per click (PPC)

PPC = Google Adwords.

BUT... as matter of fact, not all the visitor will clicks the Ads in Google SERP.

So in order for Google to maximize the revenue they syndicate this Ads on publisher website/blog.

That is what we call Google Adsense. Google Adwords Ads appear in publisher website.

If visitor click that Ads on publisher website, Google will charge the advertiser and share the revenue with you.

Hope this simple explanation help you to basically understand what is Google Adwords.