To get technical there are three action types. Short, long, and magnum.
Short actions are just that, shorter than the others. The bolt doesn't need to travel as far backwards before ejecting and picking up another round than a long action. They are also suppose to be lighter than the long and magnum actions but anymore they are pretty much all the same provided that the rifle is offered in both types.
A .308 Winchester is a example of a short action along with quite a few others including some of the newer short magnums.
A .30-06 is a example of a long action along with the others in it's class. The case is longer than the .308 Win. Some of the cartridges in this family are the .270 Win, 25-06 Rem, along with quite a few others.
If you stood a .308 Win case next to a .30-06 case you would notice the difference. The 6.5 Creedmore is close to the same size as the .308 Win where the .25-06 is the same size as the .30-06...