Pusher prop - puller prop
Clockvise or counterclockvise
There are different reasons to use the both.
If you are looking at full scale propeller airplanes you will find that the rotation differs between planes.
http://www.youtube.com/watch?v=XLStpDLc-HI
Often you will see the propellers rotate at different directions on the right and left engine on a twin enginge plane.
Brushless motors are running equally well in both directions.
Brushed motors are normally best running the "right" direction as the brushes sometimes are aftened on "arms".
For fuel engines you can sometimes (some brands) buy a crankshaft for "pusher" or twin engine installation.