Until the 2000s, price discovery happened physically. Brokers filled customer orders and locals traded their own money, all within earshot. The system's advantages were information — you could see who was buying — and its weaknesses were access, cost and the scope for abuse.
Electronic matching on globex dismantled it. CME closed most futures pits in 2015; a few options pits lingered longer.
Example: the old S&P 500 pit handled a $250-per-point contract; today the equivalent flow is in es and micro-futures on screens, at a fraction of the cost per trade.
Related: open-outcry, locals, floor-broker, globex, e-mini