This is a commonly asked question and yet sometimes poorly answered, so here's the long and the short.
Google AdWords allows you to create advertisements which appear in Google search results and/or on Google display partner websites. Each time someone clicks on your advertisement you pay Google some Benjamins 🙂 With Google AdWords you pay Google.
Google AdSense enables website owners (as well as YouTube channel owners) to display Google AdWords advertisements on their websites/channels. Each time someone clicks on one of these advertisements you receive some Benjamins 🙂 With Google AdSense Google pays you.