In butterfly-style shooting, the shooter pulls the slingshot’s pouch back so far that their hand passes their elbow (spread “wings,” like a butterfly). It’s a way to gain shooting power. Butterfly-style shooting requires long, stretchy bands — almost always flat bands.
Flip style is another way to add power to a shot and can be used with or without butterfly shooting. To shoot flip style, draw your slingshot as usual, then flick your front wrist forward at the exact moment you release the ammo. You’ll get a more powerful shot because you’re adding a vector to it.