Mash profile question

Downloaded the trial and am loving it so far, but I do have a question I can't seem to figure out.

I am entering recipes that I will be doing 1 step infusion at a certain temp and them batch sparging....1 step under the listing.  But there are 3 choices, light, medium and full body.  

What are the differences between these?  Do they make a difference on the recipe overall?

Yes.

The mash temp has a big impact on the amount of non-fermentables in the wort which has the effect of changing the FG of your beer.  Unfortunately most recipes don't even talk about this factor.  Light body would be at the lowest temp and full body the highest.

It all has to do with enzyme action.  I'd suggest palmers book, How to brew ( http://www.howtobrew.com/section3/chapter14.html ) for a tutorial

Fred