Stop Loss (SL) and Take Profit (TP) are types of pending orders. SL and TP is an instruction, which you can attach to your Market Order at the moment you want to enter this order on the market or later on, when the transaction is already open.
By placing a Stop Loss limit, you are setting a price at which you want to close your transaction in case if the market will turn against you. Once the level of losses will reach the limit set by you, your transaction will be closed automatically. In other words, you may use SL to minimize your potential loss.
By placing a Take Profit Limit, you are setting a price at which you want the system to automatically close your transaction at the point when it will reach a certain profit. So, you may use this limit to secure your potential profits.
Stop Loss and Take Profit limits for open short positions are executed at ASK price, while Stop Loss and Take Profit limits for open long position are executed at BID price.
Please remember that slippage may apply to all pending orders. It means that, if a positive or negative slippage occurs, your transaction may not be executed at the ST or TP price set by you, but at the first available market price.