The basic function of crypto is that you can buy cryptocurrencies with dollars and sell cryptocurrencies for dollars. I suppose there are other functions? But the main thing is that if you think Bitcoin will go up, you spend some dollars to buy some Bitcoin, and then if it goes up (or doesn’t), you sell it for dollars.
If you like crypto a lot — or if you are an institutional-ish crypto trader — you will do this a lot, and you may find yourself frustrated with the dollar side of things. Crypto trades globally, 24 hours a day, seven days a week; you can use smart contracts to send crypto automatically, and sending crypto is generally a permissionless lightly-regulated activity. But if you want to buy crypto with dollars, you need to use the US dollar financial system, which can feel clunky to you, a crypto native. You will probably have to send a bank transfer, but the banks are not open 24/7, and some of them might raise annoying questions if you try to transfer money from your bank account to buy crypto.
