Overgrips, what do they do?

I have bought a new racket, and it just doesn't feel right. My $29 racket feels a lot better in my hand. My highschool coach likes the $29 Wilson compared to the $120 Dunlop. Well anyway, someone suggested I get an overgrip. I went and bought three at the local sports store and put one on the racket. I will check it out(play) tomorrow. But I have a question. What are they suppose to do? Also, I noticed that a lot of players seem to have them on their rackets.

I hope they give you a better a grip on the racket.;)

They're particularly useful if you're sweating a lot and your hand get slippery

WEll, an overgrip doesnt do much when the racquet grip is new. Overgrips are put on usually for softness or tackiness. The prob is prolly in the racquet itself :)