On a new Mac, the Dock is a static menu at the bottom of your screen. It’s basic. It works. When you’re ready for a little more flair, you can customize your Dock to do some neat tricks like magnification (so it gets big when you mouse over it) and auto-hiding (so it only pops up when you move your mouse to the bottom of your screen).
If you’d like to resize the Dock, you can do so in one of two ways. The first is to click and drag the dock separator (see image). Dragging upwards will increase the size of the dock, while dragging downwards will shrink the dock. When you find a size that works, release your mouse button. You can also resize the Dock by accessing its preference panel inside System Preferences. The benefit to using System Preferences is that you can set the normal size of the Dock and the magnified size.
Bonus Tip: There’s a hidden animation for minimizing and restoring apps, called “suck”. Find out how to enable this feature here. (Source: OSX Daily)