I took some where here; Adwords is Google's program for advertisers whereby you can post advetisements for a fee. Your ad will be displayed on the search results page and content pages on other sites that choose to display Adwords ads on their sites. You only pay when someone clicks on your ad. Adsense is the program under which information publishers (web sites with suitable content) can opt to display Adwords ad on their sites. If anyone clicks on these ads, the web site owner's Adsense account gets credited by a percentage of the fee that the Adwords advetiser pays to Google. Any other though, dou you have a more simple word to describe? Pls don't give me funny or joke thing..
How about: AdWords users pay for Google Ads, AdSense users earn from Google Ads. That's about as simple an explanation as you can get.