Will I buy a stock for less then the limit order?

Im completely new at stocks as you can tell. I understand if you put a limit order on a stock it will buy it for that price or lower if it hits in that range. If I put put a limit order on a stock and it opens for less will I buy it at the opening price or the limit order price? The reason I say opens is because I do all my research and buying after market hours. Please help me!!! lol