Physics problem... Stumped

Fg=G(m1m2/r^2)

That looks correct from what I remember, but what does the big G stand for.

Also, if I remember correctly, the satillite is accelerating. The change in direction does count as acceleration, even if there is no change in velocity. Just as the moon is accelerating around the Earth. I always liked physics, just when it got into electro-magnetics, it was over my head.