Basically if you find a topic interesting, +1 buttons let people who love the page's content recommend it on Google search.
In short, its a "Like" button, as on facebook. (ps i hate facebook, ish)
In the long run it will help us in google results and bring more members in
So if you like the page your on, for whatever reason (funny, good guide, usefull info, etc) "+1" it
Ps you will need a google account to be able to do it.