Google AdSense is a free, cost-per-click ad network through which publishers display programmatic ads from Google Ads advertisers.

Indie Ads Manager is an ad-serving platform that allows you to quickly and easily manage all of your online ad campaigns, including campaigns from AdSense.

The key difference is that AdSense is a way to help publishers earn money through website monetization using programmatic display ads, but you are not able to manage your overall ad inventory.

Indie Ads Manager allows you to manage all of your ad inventory (direct sale and programmatic), perform scheduling, weighting and prioritization of different types of ads, and more.