Here's what Heart Scales are used for in the Pokemon games:
* Evolution: Certain Pokemon evolve by using a Heart Scale along with a specific move. For example, Roserade evolves from Roselia by using a Heart Scale and teaching it the move "Magical Leaf."
* Learning Moves: Heart Scales can also be used to teach a Pokemon a move it wouldn't normally learn. However, this typically requires visiting a move tutor or specific location.
Catching Pokemon requires Poke Balls and weakening the Pokemon using attacks or status conditions. Heart Scales have nothing to do with catching them.