Fly fishing is the art deception. You can't just trick a fish into biteing anything. that is why people decided to try and create thing that looked apatizing to a fish.
These hook they created are called flies. flies come in many different size, shape, and colours. They are made to look like anything from an ant floating on the surface to a larva that has just hatched.
I have just recently come to love trying to trick fish by tieing flies. That is why this sight is devoted entirely to this