MRPG Hit Points
The basic system is thus: you have a certain number of hit points. If that number reaches 0, you die. Every character's base HP is equal to 100 + (STA x 10). Various classes and other abilities get bonuses.
Base HP represents the maximum number of hit points you can be healed to.
Damage and Buffs
Any time the STA changes, the max HP also changes. If the number goes down, they take damage, even if their health was not full. Example: a character has 10 STA, base HP is 200, but they are at 180. They take 1 point of STA damage. This drops the Base HP down to 190, but they ALSO loose 10 HP from their current hit points. This can get rather painful.
All stat damage is temporary. But when the damage is reversed, they do not receive healing. The same is true with equipping an item that improves the STA stat or adds additional base HP. Example: a character has 10 STA, their base HP is 200 with no damage. They equip an item that adds +4 STA. Their base HP increases to 240. Their CURRENT HP remains at 200.
Some items improve your HP by adding to the STA stat. Others improve it more directly by adding to it. Any time an Equip Item lists an HP bonus, that adds to your Base HP.
All restorative abilities heal for a percentage of maximum hit points. They do not "heal a percentage" but FOR a percentage. So, if a character has 100 max HP, and they are currently at 50 HP, drinking a potion 10% healing potion would heal them for 10 points, up to 60 HP.
Percentages are added to each other, not to the total healed. So, if a player has an ability which makes a potion heal for 10% extra, that 10% gets added to the potion's base effect. Let's say they have that ability and they drink a 20% potion, it would act is though it were a 30% potion.
Spells like Heal work the same way, on a base percentage of maximum. Any type of healing amplification stacks with the spell, again it stacks with the base percentage(10% healing amplification on a 20% spells heals 30%).
Healing potions always heal by percentage(10%, 50%, etc). This is percentage of base. If a character has a base of 200HP, a 50% potion heals for 100HP.
There are also potions and effects that add additional "temporary" hit points. These can go over and above the Base. Now, this only happens if the base is full, but basically you can have a more or less infinite number of hit points.