What It Means
Ask price (also called the offer price) is the lowest price a seller is currently willing to accept for a stock or option. It sits opposite the bid price, which is the highest price a buyer is willing to pay — together they form the bid-ask spread you see on every order screen.
How It Works
When you place a market buy order, you get filled near the ask price, not the bid. The gap between bid and ask is the spread, and it isn't fixed — it widens when a stock is illiquid or during volatile moments, and narrows when a lot of buyers and sellers are active.
Example
Suppose Reliance shows a bid of ₹2,845 and an ask of ₹2,846.50. If you place a market buy order, you're filled around ₹2,846.50 — the ask — not the ₹2,845 a seller would have to accept. That ₹1.50 gap is the spread, and it's the quiet cost of trading at market price instead of setting your own limit.
Warning
Placing a market order on a thinly traded option can mean your fill price is several rupees away from the last-traded price shown on screen — the ask can be far higher than what you expected if the order book is thin.