Can someone explain to me the difference between a 108mm and a 113mm bottom bracket?

Recently I purchased a combo on a Raceface Evolve crank and an Evolve Bottom bracket. My exisying cranks are in bad shape, and my existing BB makes a grinding noise.

The new BB is 113, and the directions for the new crank says to use a 108mm only. They dont even sell a 108mm evolve bb.