What's the different of "opt-out" and "blacklist"?

[ohho]

I found an option "Mark recipients as Opt-Out" in Import process settings. What's the difference between "Opt-out" and "Black-list" recipients?

Thanks

[maschoff]

A recipient with status "opt-out" may opt-in again. A recipient with status "blacklisted" can not opt-in again but is filtered.