Order Book
The real-time record of all outstanding buy and sell limit orders for an asset, organized by price level.
The order book (or limit order book) is the exchange's live ledger of resting buy and sell orders. Bids are stacked below the current price; asks are stacked above. The inside market — the best bid and best ask — is the Level 1 quote.
The depth of the book reveals where large concentrations of buy or sell interest are clustered, which traders use to anticipate support, resistance, and potential price magnets.
Order books are dynamic: orders are added, modified, and canceled hundreds or thousands of times per second in modern markets.