system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: We all know those movie scenes of Wall Street where people are yelling at each other while talking on phones. What exactly is going on there?
gpt
Before computers became the primary method of matching buy and sell orders, "pits" where broker-dealers conducted transactions face to face were the norm.  Only a small portion of the trades would go through the pit, but by tracking the action in the pit a "market price" could be established that allowed trades to clear with mutual agreement of buyers and sellers outside the pit. (People could write a contract that said "do a trade at the price in the pit as of noon on Thursday", etc.)

The action in the pit was either someone saying "I want to sell X at Y price" and hoping someone would buy, or someone saying "I want to buy X at Y price" and hoping to find a seller.  Shouting out those offers repeatedly with minor changes in price let the rest of the pit know what kinds of deals were available.  A buyer and a seller could hear that each other had a trade they wanted, and then they'd make a connection usually with hand signals (and even more shouting) to confirm the trade.  The result was a piece of paper with the details written on it that was taken to a desk in the pit area where the trade was recorded and published.

These pits were not perfect.  People in them could and did influence prices by apply various social (and sometimes physical) pressure to their counterparties.  It was a huge clash of personalities and the strongest personalities could sometimes "move a market" by getting other buyers and sellers to go along with their desired price momentum.  Getting rid of these issues was a big reason people moved to computerized trading.