Market vs Limit Order
Market = buy now at any price. Limit = buy only at your price.
Market order executes instantly at the best available book price - guaranteed fill, but in thin markets you can pay way more than you see (slippage). Limit waits for your level - you control price but no fill guarantee. Best practice: always limit for big sizes; market only when truly urgent.
In plain words
Market: buy now, don't care what it costs - fast but in thin markets you pay way more than the screen shows. Limit: only buy if price drops to 65k USD.
Example
Market buy 1 BTC during a pump: 70k on screen, filled at 70.5k = 500 USD slippage.
Also known as: market order, limit order