Google Ads is used by advertisers and AdSense is used by publishers.
Google Ads is used by advertisers for advertising whatever they want like products, meanwhile, Adsense is used by the site owners to put ads on their site for example a blogger wants to earn money by publishing quality content on his/her site. with the help of AdSense ( if got approved) google will put ads on his/her site in return you will get $'s.
~poor English but I hope you understand what i was trying to say~