AdWords is the Source of AdSense Income

AdWords ads are the source of all the AdSense income you are
able to generate. As a result, you need to fully understand
the AdWords system in order to appreciate how the AdSense
system works.

Google describes AdWords as "a quick and simple way to
purchase highly targeted cost-per-click (CPC) advertising,
regardless of your budget." These paid ads (sponsored links)
are displayed by Google on the search engine results page
along with the non-paid (natural results) for a given keyword
search.

In order to create a Google AdWords ad, it is necessary to
specify what keyword or keyword phrase must be input by the
visitor before your AdWords ad will be displayed. In addition,
you need to set the maximum amount that you will pay to Google
for each click on your AdWord.

There is a nominal activation fee but Google does not have a
minimum monthly charge. Google provides an account Control
Center that allows you to track the performance of your ad.
The ad will be displayed within minutes to the searchers after
your account billing information has been submitted to Google.

AdWords ads must adhere to specific Google requirements. The
title can contain up to 25 characters, the ad text can have
up to 70 characters and the display URL must be less than 36
characters.