A market order buys or sells immediately at the best price currently available. A limit order only trades at the price you set or better, so you control the price but the trade may not happen. A stop order waits until the share reaches a price you choose and then becomes a market (or limit) order.
Market order
Use it when getting the trade done matters more than the exact price, for example for a large, heavily traded share during opening hours. In quiet or fast-moving markets the price you get can differ noticeably from the last price you saw.
Limit order
You state the highest price you will pay (or the lowest you will accept when selling). The order waits in the order book until it can be filled at that price or better, or until it expires. Limit orders protect you from paying more than you intended, which is especially useful for smaller shares with a wide gap between buying and selling prices.
Stop and stop-limit orders
A stop-loss order sells when the price falls to a level you choose, to limit a loss. It becomes a market order when triggered, so in a sudden drop it can be filled well below your stop price. A stop-limit order avoids that by becoming a limit order instead, but then it may not be filled at all.
Whichever order you use, check the share's currency, the number of shares and the total amount before you confirm.
This content is general information, not investment advice.