Health and Mana in Ragnarok Online and Ragnarok Online II are the most basic elements that allow a player character to survive and thrive in the game world. Each and every playable character created in both games have a certain amount of health and mana, which can be increased with base level, health buffs, and appropriate gear.
Health in RO and RO2 refers to Hit Points (HP). HP determines how many hits your character can take before it dies. The more HP your character has, the longer it can last in combat.
The stat responsible for modifying the HP of a character in RO and RO2 is VIT.
Mana in RO and RO2 refers to Spell Points (SP). SP determines how many times you can use certain skills as each skill consumes different amounts of SP. The more SP your character has, the more skills it can use at a time.