What is the difference between an edge loop and an edge ring? I've heard the terms "edge ring" and "edge loop". What do they mean and how are they different?
Edge Loop
An edge loop is a series of directly connected edges:

You can select an edge loop with AltRMB.
Edge Ring
An edge ring is a series of edges which are not directly connected, but share faces:

You can select an edge ring with CtrlAltRMB.

As a bonus, you can run the select edge loop or the select edge ring operator on every selected edge automatically by pressing Edge loop or Edge ring in 3D view &gt; Header &gt; Select.