A subtle question, eidolon. Here is one set of opinions.
A curved line is a single curve, probably smooth and indeed somewhat elegant in form. Imagine the curve formed by a rope hanging loosely between two poles or a necklace hanging around the neck of a pretty girl. Curved lines are aesthetically pleasing. ) (
A bent line (not bended) may not be curved at all, but could be a line with a sharp immediate change of direction. Imagine a stick that is broken, but not broken in two. > <
A wavy line has many small curves, up and down or backwards and forwards.
Join these up ~~~~~~~