This is because an international merchant accounts allows you to accept payments through credit cards issued by banks outside of your country's borders. These include Visa, MasterCard and American Express (AMEX). Additionally, some providers will even allow you to accept cash-based transactions such as PayPal or Apple Pay if they have been set up with this feature enabled on their end.
https://yourmercha.mystrikingly.com/blog/the-pros-and-cons-of-using-an-international-merchant-accounts