How is the area behind a brick exterior wall waterproofed?

I have an 100 year old house. I'm having some remodeling done and my contractor told me he doesn't think my exterior (brick siding all across) is waterproofed. I'm not sure how one can tell without the ability to look behind the brick but he said something about that if it's waterproofed, there should be some stuff at the bottom of the brick along the perimeter - it went over my head so idk what he was referring to.