If your email ends with @privaterelay.appleid.com, it means you used your Apple ID to create/sign in to your account.
Apple has a feature called Hide My Email, which provides users with an automatically generated email address (like the one you’re seeing). So this simply means that you have Apple as sign-in method.
You can read more about how it works here on Apple's FAQ: https://support.apple.com/en-us/HT210425