You use a "fly" as bait. They are not real flies, but they look like flies and have a hook built into them. You use a different kind of fishing line as well. It is very thick and usually bright yellow. You kind of flick the line over your head and into the water so the fish think the "fly" is landing on top of the water. It is usually done in moving water, like a mountain stream or something similar. People will wade into the stream to fish.