Let's say I want to trade a large amount of $TICKER. Sometimes, just sending a buy order is not ideal as it might drive prices up. So you start calling brooke

Let's say I want to trade a large amount of $TICKER. Sometimes, just sending a buy order is not ideal as it might drive prices up. So you start calling brookers and hope they help you by finding other folks who want to sell large amounts of $TICKER. They also might spread orders over a larger time frame. That's just an example, but overall the chat is used to negotiate assets. Buying and selling stuff is often a very manually coordinated process.