From Traderpedia

Definition: The place at an exchange where floor traders trade.

The pit is usually an octagonal shaped series of steps, with a flat, lower area in the middle and then a series of steps raising up around the edge.

Floor brokers and the biggest locals usually stand on the top step, and other locals lower down the pecking order will stand progressively further into the pit.

The CME Eurodollar pit is one major exception to the octagonal shape, being shaped like a longboat.