The rate at which health regenerates per second is referred to as health regeneration.
The Base health regeneration for all classes is always at 25 HP / second but can be further increased by a variety of Gear that has the "Restores x amount of Health per second" stat on it.
Health Regeneration isn't the only way to restore your health, some other methods include:
- Healing Spells
- Some Offensive Spells (ex: Lich's Parasite)
- Life steal that is obtained as a stat from Gear