Factor in error estimate and Tolerance factor

Hi,
I am new to comsol. I was using fluent, but could not get things done there. Now when i start using comsol, i try to link
things to fluent inorder to understand. In fluent while solving, we give residual, which is factor in error estimate, also there is under relaxation factor, i couldnt find those in Comsol. Even though i got the solution, i couldnt understand what is happening. Please someone help. Thanks