Curling ice is grainy, like an orange peel. Otherwise the rock would suction right too it and get stuck. The granite stone is found in a a specific Scottish quarry and weighs between 38 and 44 pounds. The brooms are to direct the stone in a specific direction in order to heat the ice in front of it and direct it's path. The more water beads on the ice, the faster the stone will travel.
I'm not sure on the scoring but think of it like shuffle board.
Google it, it's quite interesting. This year, we have a pregnant Olympian on one of the teams. That doesn't happen very often.