Googles adsence is a Google product which help users to earn money online. The users has to display the ads on their websites, social media , or blogs. When a visitor click on the ad or according to the type of the ad you get paid. The ad can be anything.
1. To start an adsence account you must be 18+.
2. You must be the owner of the site.
3. You can't published plagiarised contents.
4. You have got enough views.
5. You get paid only when you reach 100$. 
Google adsense provide to chance earning money online, you can earn money from google adsense by pacing ads and if you have website like:- blogging and news sites. And your website are getting organic traffic, so after that just you need to create account on google adsense and then add your website URL for getting google adsense approval and after monetization website, you will be able to serve ads on your website.
And google adsense serve different types of ads like:- text, image, video and many more. When user will come on your site and after that they click on ads, by clicking you will able to generate your revenue.
And you can also earn money from youtube, because there are option available to monetize youtube channel, and after monetization you channel you can place and serve ads your youtube videos content. In the youtube you can place two types of ads skippable and non-skippable.
Also Read :- What are the criteria to get approval for AdSense?
AdSense is a way for publishers to earn money through online content. AdSense works by providing with ads to your website based on your quality content.The advantage of adsense is you can get highest paying ads on your site for which you get paid but you want this advantage on your website you should have to create a quality content which should be helpful for others,
Use different types of ad units.
Also Read :-What are the criteria to get approval for AdSense?