Edge Loops

How well a model is created determines the quality of the whole animation sequence that it’s intended to be used for. This is because how the faces in the polygon mesh are positioned determines the models flexibility. Creating 'Edge loops' is a technique that allows one to create the most efficient and economical model possible. It’s a manner of organizing polygons so that the model has as much form as possible with using the least amount polygons. They are also used to allow facial features to be more flexible and limbs to bend without them appearing unusual.

According to a comment in a forum edge loops are "a series of connected edges following a unique symmetrical path" and "The idea is the edge loop continues as long as there is a middle path to follow between two paths that its doesn't follow". Facial edge loops are "a series of quad faces connected through their opposite edges".

Faces are connected to each other in a circular manner around facial features such as the eyes, nose and mouth. The other edges follow the form of the rest of the facial features. They are created this way so that when facial expressions are animated; there will be no unnatural deformations that would make the character appear less naturalistic and believable. Edge loops are also placed around the circumference around joints so that when any limbs bend in an animation, there are enough polygons to accommodate the change in shape. This is also to enhance movement of characters and make them more believable.

To create edges loops, one can use the ‘add edge tool’, which allows one to draw the correct pattern of edges in the polygon mesh. One should then delete the excess edges, which also saves a model from containing unnecessary polygons.

Works Cited:
http://blenderartists.org/forum/showthread.php?t=101859