What is Google Ad Manager and how it is different from Google Adsense?

Google Ad Manager is a unified platform which Google has made for the publishers to manage their ads across the various devices used by the readers or the users while viewing the published contents in the publisher's site. Earlier Google had two programs for doing more and less the similar thing and they were DoubleClick Ad Exchange and DoubleClick For Publishers (DFP) but now these two are merged into Google Ad Manager. So, the publishers can now monitor and serve the ads in such a way as to maximise the revenue through advertisements. So, Ad Manager is a management tool that can be used for analysing the traffic, views statistics etc and actions can be taken to change the Ad serving in a particular pattern. It is a higher level platform with so many built in functions and one has to learn it thoroughly if one wants to benefit by it in one's business.

On the other hand Adsense is a program where one has to apply for it for one's site and it will display ads in it and the site owner will share the revenue with Adsense. Site owner will not manage the ads, they will be managed by the Adsense team only.

1. Google AdSense gives us the opportunity to earn money from our websites. It's a cost-per-click program. The publishers will earn money from clicks made on the ads displayed on the website, It is easy to set up Adsense and no additional technical skills are required. Auto Ads are also available. It is a self-serve platform and free.
2. Earlier Google had two separate programmes called DoubleClick For Publishers (DFP) and Google Ad Exchange. Now they merged the two into a unified platform and called it Google Ad Manager (GAM). On GAM one can streamline their ad operations. The operations include the definition, sales, and optimization of direct, third-party networks and programmatic deals for all devices. It is a central platform to monetize all types of as inventory. This programme will give you the highest price.
3. Adsense allows you to run the ads from an advertiser who is with Google only. But Google Ad Manager allows you to run Ads from Google advertisers and also local Advertisers. You can use the same to promote your own specific product on your site.

Google Ad Manager is an ad serving platform that helps make your ad management easier by bringing all your traffic needs in one place. By linking your Ad Manager account to Analytics, you get a mixed view of advertising revenue and user behavior to improve your earnings strategy.
Publishers use Ad Manager to display advertisements. Also, use Google Analytics to understand user behavior. No system has significant information about the relationship between these two areas - how user behavior affects revenue and how advertising affects user behavior. Ad Manager publishers can view reporting linked together between Ad Manager and Google Analytics 360 in the Google Analytics UI from Ad Manager Reporting Integration. This is a mixed report that shows Ad Manager impressions/clicks/revenue, separated from the source of traffic or a particular page.
Google AdSense shows publishers how to make money from their online content. AdSense works by matching ads to your site based on your content and people visiting the website. People who want to advertise their products, make these advertisements, and pay for them. These advertisers pay different prices for different advertisements, so there will be a difference in your earnings from them.