I was looking at airfare codes and saw that there's an airfare code for First Class Premium and one for First Class Discounted.
What does First Class Premium offer that First Class Discounted doesn't?
They are just the same as various airfare classes in the economy section. Everyone sits in the same area, they get the same food, they check in the same line, they get the same drinks, etc.
The difference lies primarily in the fare rules, can you change your reservation for free or for a fee, can you get a full refund or not, do you have to book so far in a advance or the right up to the day of travel, etc.
And these rules vary from airline to airline so there is no single definitive answer