Ok, so I know that anything that has mass has gravity. And gravity is the attraction between objects. But, how does this work? What causes gravity?

If the bigger an object is, and the more gravity force it has, does this mean everything will eventually be pulled into one huge...thing?

I mean, is Earth and the planets going to be sucked into the sun one day, then the sun going to be sucked into the middle of our galaxy or something? Then the galaxy sucked into something and eventually the entire universe even be sucked into something? What do you think?