The white face is the key to the ID of this fly.
As for the differences between flies and bees, the number of wings is important for taxonomic purposes and evolutionary reasons, but the difference is nearly impossible to see in the field or even in a photo, for one thing, bees and wasps usually hold their wings together so they appear to be only two, for another,only occassionally do you get to see the halteres of a fly. Familiarize yourself with other physical differences: size of eyes, antennae, thickness of legs, general body proportions, flight pattern and you will have no trouble.