In order to be able to take online payments for your goods and services you will need to register with a Payment Processor. This is a company like Paypal, Realex or Stripe who verify and take the payment from a customers credit cards for you. They take a small commission (eg 3.5%) and they make those funds available for you to draw down to your bank account. By using these payment processors it means that you never have to manage the credit card data directly your self (GDPR) and these companies can handle millions of transactions per second from cards all over the World. It pays to do some research on what fees and how often they payout to your account as there are all slightly different.