Are wallet addresses in the crypto exchange website actual ethereum accounts?

a newbie here, I am trying to understand how ethereum based CEX's work. Users create accounts/wallet addresses (not email-linked user accounts) on the exchange. Are those addresses actual ethereum accounts from the mainnet?

I am asking this because this particular exchange has about 1000 users, but when I type eth.accounts in geth console, it shows only one ethereum account, which I assume to be the exchange account. Shouldn't there be 1000 accounts? How does the exchange handle it when a user deposits/withdraws from the exchange to the external account in the mainnet?

or should I use a different geth command?