I opened two nasdaq BUY trades on Friday and didn't close them before the market closed for the weekend so the trades were stuck in an open position over the weekend. I woke up on Monday around 2 am to find out the market opened lower than it closed causing a gap, This meant the price jumped over my stop loss without triggering it and so the broker activated the stop loss at the next available price which of course was a bad price for me. I incurred a loss on the trades because of this so called "gapping".