The dimples are the indentations on the golf ball that help the ball travel through the air. They reduce the resistance of the wind.
If the ball is heavier, the ball will travel farther, but that doesn't mean you have the most control of it. A lighter ball will go shorter, but you can control it more.
Hollow or Filled
Golf balls come in both varieties, but hollow balls are used primarily as practice balls on the driving range. Hollow balls are not allowed on the PGA Tour.
Hybrid Golf Balls
You will find hybrid golf balls in several variations such as a heavier ball with less dimples or a more dimpled ball with less weight.
When the ball is struck, it changes shape and reforms itself. Over time, the ball's shape will change permanently, which is why you should change balls after a couple holes.