Definition
The documentation defines it as an order that executes at the selected limit price or better. Three options decide how long it may wait: good til cancel rests on the book until it is filled or cancelled, post only is added to the book and is only executed as a resting order, and immediate or cancel is cancelled if it is not immediately filled. A limit price that crosses the book does not wait at all: it fills at once, as a taker.
A limit that rests is the only way to be a maker, and that is most of the reason to use one. At the base perps tier a maker pays 0.015% of the notional where a taker pays 0.045%, and a maker providing more than 0.5%, 1.5% or 3.0% of the 14-day maker volume is paid a rebate of 0.001% to 0.003% on each trade instead of a fee. The price has to be on the market's grid: an integer multiple of the tick size, at most 5 significant figures and at most MAX_DECIMALS - szDecimals decimals. The maximum limit order value is ten times the maximum market order value.
What a limit order does not give is a fill. It can be passed by, and a price that merely touches it is not a certainty either: resting size at a level is not always taken when the market reaches that level and turns. Our replay counts a fill only once the price has gone through the level by the charter's throughBps, 0 by default and 5 basis points in the pilot's own charter, for exactly that reason. The pilot's ladder is made of limit orders resting on Hyperliquid, and the whole position leaves on a single limit at the average price plus 10% of the base stake.
Example
An example, in round figures. With the best ask at $100,000, a limit buy of 1 BTC at $99,000 rests on the bid and fills only if the price comes down to it. If it does, the fee at the base maker rate is 0.015% of $99,000, so $14.85, against $45 for a taker filling 1 BTC at $100,000. If the price never comes down, the order costs nothing and the trade never happens.