Free for services that use Sign in with Apple. Need iCloud+ for generating addresses outside of that.
Also, 99 cents a month for the cheapest plan isn’t too bad for everything it gives you. If you’re in the iOS/Apple ecosystem, it’s a worthwhile purchase.
It's created automatically (or manually) for any email prompt. It is automatically set for the domain so fill in provides the forward address automatically. You can turn this off and you can delete the forward address anytime you want.
A disposable email in the form provided by this service, the emails essentially go into a black void. They don't go to your normal inbox like the ones provided by Apple do.