There are basically two kinds of exchanges-

1. Fiat gateways ie Coinbase and Gemini, where you connect a bank account and can buy in dollars
2. Crypto exchanges pretty much 99.9% of exchanges, but you do not connect your bank account so this is safer for you becasue most of them dont even really ask form much in the way of verification, Kucoin is just a Crypto exchange with no fiat gateway.... But it is valueable to be on a lot of exchanges becasue sometimes they close memberships and you cannot even get in, thats why people were offering $4,000 to anyone who would sell them a Binance account, becasue they closed signups