Immune and protect mean the same thing. They share an entry in the REG:
Immune and protect abilities keep the target from being affected by the strength on cards to which it is immune
or protected, keep the target from being able to be targeted by cards to which it is immune or protected, and also
allow it to be unaffected by game rules which would normally affect it.
Confusingly, however, the REG also includes the following:
Immune and protect are targeted separately by abilities based on the name of the ability referenced. A card
that negates immunity will not negate protection, and a card that is regardless of protection will not be able to
affect an immune target.
So immune abilities and protect abilities differ in one thing only: name. Everything about how they work and how they're played is
exactly the same, but a card that negates immune abilities does not negate protect abilities, and vice versa, and "regardless of protection" does not mean "regardless of immunity".
Which is just plain silly, if you ask me.