![](https://s3-eu-central-1.amazonaws.com/euc-cdn.freshdesk.com/data/helpdesk/attachments/production/80040225150/original/L_cDKVuMykhV3gL91WjyrXTx73ClLo9Qzw.png?1632821359)
An order book contains all outstanding buy or sell orders for an asset, organized by price level. An order to buy is called a ‘bid’, and an order to sell is called an ‘ask’. The exchange’s matching engine pairs up bids and asks with market buy/sell orders, resulting in a trade.