A buy or sell market order triggered at a set price threshold. Stop Limit sell orders are also known as a "Stop Loss" orders.
1.1 stop limit buy
Carol wants to buy $1000 USD of BCH, but only if a bull run is confirmed. Carol sets up a stop limit buy order for $1000 USD with the stop set at $1000 USD/BCH, currently the price is at $800 USD/BCH. Carol's order will not execute until the price reaches $1000 USD, at which point Carols market buy order will be placed. Go Carol.
1.2 stop limit sell
Carol wants to set up a stop loss order as insurance against the price drastically dropping while Carol is on vacation. Carol sets up a stop limit sell order for her 5 BCH at $699 because she believe that if the price drops below $700 it will go down even further. If the price hits $699 Carol's stop loss will execute and a market order selling 5 BCH will be placed. Should of hodl'd, Carol.
* All terms and definitions may update as the Cryptionary improves.