Thanks, Alix, but that doesn't really explain anything -- to me, anyway.
This feature will replace the older "Reputation" feature. The Thanks feature is a more positive and visible system for members to express their appreciation for your contributions. You will be able to view the comments in your User CP and, if you like receive a PM when you receive a Thanks.
As far as I recall, the "Reputation" feature did all that, and it was fun. Why fix something that wasn't broken?