How do cryptocurrency aggregators work, the mechanism for depositing / withdrawing funds on exchanges?

Question

Cryptocurrency

Each user generates their own crypto wallet for each currency. The user makes a deposit for the selected cryptocurrency, then makes an exchange for another. And when he withdraws it, where do the funds come from? Is it from a common intra-service reserve or are several transactions made from different accounts (or from one, if enough)? Where can you read about something like this?

Answer 1

There are cold and hot wallets on the exchanges, usually the crypt comes to users and they transfer to a common wallet and withdraw from it