Fill
The execution of an options order at a specific price.
Explanation
A fill occurs when a buy order matches with a sell order. The fill price can be at the bid, the ask, or anywhere in between (price improvement). Limit orders specify the maximum (buy) or minimum (sell) fill price, while market orders fill at the best available price.
Example
You place a limit order to buy a call at $2.30. The order fills at $2.25, giving you $0.05 of price improvement.