The main thing about the Google platforms Adwords and Adsense, is the unique relationship that they have with one another. Adwords and Adsense have a relationship in regards to the publishers and the advertisers using each of their platforms.

The Adwords platform is used by means of obtaining traffic to your website through their PPC method. Adsense is best used by publishers who get paid for publishing Google ads on their website related to their keywords and industry their content is promoting within your website or blog.

Now you can use both the Adwords and Adsense to make money. This is called Adsense arbitrage. What you are doing there is paying for traffic per click in hopes of making a profit when someone clicks on one of our adsense ads obviously paying more than the click it took them to get there. You will need to be careful with arbitrage because Google have policies and counter methods regarding this strategy thanks to marketers  abusing this method in the past.

This change is greatly affected by the Panda rules and other search engine changes that have taken place with Google. None the less, there really isn't so much a difference between Adsense and Adwords as much as it is about the relationship between the two platforms from Google.