Most traders only use market and limit orders. But your broker offers time-in-force and fill conditions that control how an order is filled — and on wider, thinner options they matter more than you'd think.

The three conditions

IOC — Immediate-or-Cancel. Fill whatever is available right now at your price, and cancel the rest instantly. You might get a partial fill. Good for grabbing available liquidity without leaving a resting order hanging.
FOK — Fill-or-Kill. Fill the entire order immediately or cancel all of it. No partials, no waiting. Use it when a partial position is worse than none.
AON — All-or-None. Fill the full size or don't fill — but unlike FOK, it's willing to wait for the whole quantity. You avoid partials at the cost of maybe not filling for a while.

Plain limit orders can fill piecemeal. These conditions let you say “all of it, or none” — which on a thin strike is often what you actually want.

When they help

On liquid, near-the-money SPY strikes you'll rarely need them — there's enough size to fill a normal limit cleanly. They earn their keep on thinner, wider strikes, where a plain limit can fill in awkward pieces at drifting prices. FOK or AON keeps you from ending up with a half-position you didn't want; IOC lets you take what's there and move on. For fast scalping, though, the deeper fix is to trade liquid strikes in the first place, and to let your platform route the order. Also mind your time-in-force so a working order doesn't outlive the session.