In a stop loss limit order a limit order will trigger when the stop price is reached.
To use this order type, two different prices must be set:
Stop price: The price at which the order triggers, set by you. When the last traded price hits it, the limit order will be placed.
Limit price: The price you would like your limit order to fill at. Your order will be filled at this price or better.
Example: You have a long position on BTC open and the current BTC/USD price is 8000. You don't want to close your position below 7900, so you open a stop limit order with the stop price set to 7950 and the limit price set to 7900. The price falls below 7950, triggering your stop price. A limit order will then be opened to fill at 7900 (or better).
It is important to note that your stop loss limit order is not directly tied to a position (not reduce only) but is an independent order and if you exit a position in an alternate way the stop loss limit must also be manually cancelled.
Note: Limit orders that execute immediately are treated as taker orders and will incur taker fees.