Look in your bathroom where the tub meets the floor. There was a gap there because the tub isn’t perfect and the floor isn’t perfect AND because the floor isn’t the tub and the tub isn’t the floor (in other words there is a gap because they are not one and the same.) You probably can’t see the gap too well because someone, probably the builder or maybe the owner, filled in the gap with caulk. Caulk is good for filling gaps because it is sticky and elastic.
Ever notice there are gaps between you and other people? Now gaps aren’t the problems, but what we fill them with can be. The best thing to fill a gap between two people is love; it’s sticky and elastic.