Upgrade Points: Those points are accumulated when upgrades fail. When you reach 100%, upgrade is sure and you will obtain +1 on your hero without any risks.
There are two other things you can find in hero tab:
Skill Icons. You can click on the icon to read the accurate description of the skills available for that character, with relative countdown.
Items. Each hero can equip three kind of items: weapons, armours, accessories (not available yet). For more info about equipments click here .