Order Book
Plain English
A list showing all buy and sell orders at different prices. Buy orders (bids) on one side, sell orders (asks) on the other. When orders match, a trade happens. The "spread" is the gap between highest buy and lowest sell price. Tighter spread = more liquid market.
Technical
Real-time registry of limit orders organized by price level, showing market depth and liquidity. Bid side shows buy orders (demand), ask side shows sell orders (supply). Order book DEXs (Serum, Phoenix on Solana) match orders on-chain. Metrics: spread (best bid-ask difference), depth (liquidity at each price), order book imbalance (buy vs sell pressure).