washcloth-for face, hand towel-for hand, bath towl-for body

and the thick elongate one is for the floor right in front of the bath tub or the shower stall for stepping on with your wet feet.

The square, small one, is for washing face.
The long shape, medium size one, is for drying hands after you wash your hands.
The bath towel, no need to explain.

Some Americans dont use the wash cloth as they take shower each morning and wash their faces in the shower, instead of using the sink.

There is one odd size - between the square and the hand towel, in elongate shape, is called tea towel - you dont normally see this except in some very fussy places. I cannot figure out what to do with such to this day. hahaha.