Buy or sell order that is executed immediately at the best available price.

An order that you place on the order book with a specific limit price. The trade will only be executed if the market price reaches your limit price or better.

A conditional order that combines a condition and what happens when it is triggered.

Stop-market order will be executed at a specified price. However, since it turns into a market order once the stop is reached, it always gets fulfilled. This means there’s no risk of missing the price frame and not having the order executed.
​Stop-limit order combines the features of both stop orders and limit orders, lending higher precision to the trader. In this case you have to provide two prices, a stop price and a limit price. The stop price represents the market price that, if reached, will trigger your stop order and will set the limit order. The limit price represents the worst price at which your order can be matched.

There are several use cases for stop orders:
Stop-loss allows you to limit how much you can lose on potential trade and thus helps you minimize loss and protect your profits in a falling market.
Breakout indicates the potential for the price to start moving above a resistance area, or moving below a support area.