The limit order book is not a simple list—it is a priority queue with price-time precedence. Orders at the same price are ranked by arrival time, and the best bid and best ask define the inside market. Hidden orders, iceberg orders, and pegged orders add layers of complexity that retail traders rarely see.

Key structural features:

Price priority: Better prices execute first.
Time priority: At the same price, earlier orders execute first.
Depth: The number of shares available at each price level.
Order types: Market, limit, stop, iceberg, pegged, and reserve orders.

Order Type	Visibility	Execution Priority
Limit	Full	Price-time
Iceberg	Partial	Price-time (refreshes)
Pegged	Full	Dynamic

Understanding these mechanics explains why your limit order may sit unfilled while the market trades through your price—your order lacked time priority or was behind hidden liquidity.