Foundations
The idea
A market order prioritizes execution; its price can differ from the last quote. A limit order sets a price boundary but might never fill. A stop order becomes active at a trigger and its execution can be worse in a fast market. A stop-limit combines a trigger with a price limit, increasing the possibility of no fill.
A worked example
A buy limit at 1.0900 is not filled merely because the mid-price touches that number; the executable ask and the venue rules matter.
Try it yourself
Place each order type on a demo account and inspect its trigger, expiry and execution price.
A mistake to avoid
Treating a stop-loss as a guaranteed exit price.