There is alot in Unity to learn. So the makers of Unity decided to be awesome and put full explanations of what each component does. When ever your in question of what something does. Just click the question mark in the top right corned of the component in the inspector pane.
Doing this opens up the description of the component in your default web browser. You don't have to have internet connection. Because the page is actually already downloaded on your computer. Ha ha. Making this blog look a little pointless