These are waveforms. It is really nice to see them on your timeline when you are cutting dialogue. They are not turned on automatically, you have to turn them on. However, they do take up more processing power to display them, so they can slow down the program. I frequently turn mine on and off as I edit.

Go to your Sequence menu and select Settings

The 3rd tab over is the Timeline Options tab, select that. On the lower left panel you will see a check box next to Show Audio Waveforms. Select that and there you have it!