While animating, you typically don't want to use a high-resolution model. A lower resolution speeds up the process considerably. By creating a 'proxy', you have both the benefit of animating a low-resolution version and rendering a high-resolution final version.
Lee Salvemini writes:
Hi Bart!
Here is a tutorial on how to make a proxy character that allows you to jump right into animating, no need to rush the final character to work on an animation.
I also got my SketchFab account up and running, wow is it easy to throw up a .blend! I've added the final result here:
https://sketchfab.com/models/2573b3be8371454dabe0f4c065a79cf7