Fire Protection will reduce ongoing fire damage, which is normally not absorbed by armor.
Fire Protection also reduces burn time when set on fire by
(15 × level)%. If multiple pieces have the enchantment, only the highest level's burn time reduction is used.
For example, at level 8, the player cannot be lit on fire through Fire Aspect enchantments. The only way to burn is standing in lava or fire. The initiated fire-ticks (lava: 300, fire: 150) will be canceled, and only the remaining time in the fire source will be added to the fire-tick timer.
Protection, Blast Protection, Fire Protection, and Projectile Protection are mutually exclusive.[Bedrock and Legacy Console editions only] However, if commands are used to have two or more of these enchantments on the same item, the effects will stack.