ApplePay is completely different and separate from Apple Cash. ApplePay is an electronic version of your bank issued credit or debit card saved into a mobile wallet. Apple‘s mobile wallet is ApplePay. Your bank and your smart phone connect and create a tokenized version of your card. The vendor never has access to your actual card or card number. It is safer from fraud than using the actual card. Many apps and online vendors allow ApplePay transactions. For example, I pay my cable bill with ApplePay. I no longer have to store my credit card information with the cable company. This quarter I am paying with Chase Freedom for the bonus points, but I have paid with American Express before.
Many loyalty card also have an ApplePay app. I love not having to grab my wallet at the grocery store. I have my loyalty card and credit card in ApplePay, so I can just tap my phone and go. You can also connect your Apple Watch to ApplePay.
Using ApplePay is just like using the physical card as far as how your account operates. Most (like 95%) of American Express offers even work through ApplePay. For the most part those offers that don’t work have transactions that must be completed via a website.
ETA, I do not use Apple Cash which is Apple’s “Venmo“ type function within the mobile wallet.