Order Book
دفتر الأوامر
The order book is the electronic record of all outstanding buy and sell orders for a security, arranged by price level and time of entry. It shows the quantities bid and offered at each price, with the best bid and best ask forming the market’s current spread. Trades occur when incoming orders match existing orders on the opposite side of the book.
Example
The book might show buyers stacked at 24.90, 24.85 and 24.80 and sellers at 25.00, 25.05 and 25.10. The gap between the best of each side — 24.90 and 25.00 — is the spread.
Why it matters
The book is where the price actually comes from: it is the live record of what buyers will pay and sellers will accept, and its depth tells you how much size the market can absorb.
A common mistake
Assuming the quoted price is available in any quantity. The best bid may be for a few hundred shares; a larger order walks down the book and fills at progressively worse prices.