The excellent items are special types of items. Every normal Item has an excellent version you can obtain. Usually they have a really low drop rate so another way to get them is by going on golden invasions and killing a golden monster. It will drop a Box of Kundun which usually drops a random excellent item. The excellent item is slightly better than the normal one and also provides several very good excellent options:
Excellent Options of Amor
Excellent Options of Ring
Excellent Options of Weapon
Excellent Options of Pendant