It's a website containing "virtual cork boards" where you can "pin" things that you love. You can also "follow" people and their boards, just like on The Twitter.
I've been spending lots o' time perusing the boards and pinning till my heart's content. I've started four boards of my own- one for style, one for the home, one for parenting, and one for the randoms. So much fun.
Next time you're bored and surfing the Interwebs, check it out! (And check out my boards, if you like, by searching betsey anderson, or directly at pinterest.com/betseyc1980.)