Basically, Pinterest offers you a virtual pin-board where you can pin up and share content of your interest - whatever interests you may have, you can create as many pin-boards as you like.
You are probably thinking that this sounds just like any other social site (which it kinda does), but in my opinion it is the classic pin-board style and mashed-up content cultivation which differentiates this site from the rest.
Check it out to make up your own mind and then let me know what you think.