Some pending orders such as - Stop Loss, Take Profit and Trailing Stop might be guaranteed only during market hours, as others may be executed at a different price if the market opens with a gap.
When the market is volatile or illiquid, orders such as Limit/Stop and OCO are not guaranteed and they might be executed at a price different than the one you have specified in your order.
A market gap is a difference between the closing price of one period and the opening price of the next one. Market gaps usually occur between trading sessions, such as during the night or over the weekend.
