Google jagger update

I am relatively new to seo and have heard about the google jagger update. Can anyone hear explain to me what was involved with this update? From what I have heard, a lot of sites got hurt by this update. Is that true? If so, how come?

A lot of spammy sites were hit by this update. Most real-content sites saw improvments. As usual, google made itself better.

Overall, most of my traffic is down a little (or a lot, depending on site), but my adsense revenue had remained steady. I guess that's because the traffic is better targeted now.

If you're new to the biz, then don't worry about it. Just concentrate of creating quality sites for humans, and google will make sure to send them to you.