General Protection
Protection reduces damage from nearly all sources — melee, falls, fire, explosions, projectiles — by a percentage per level, capped at Protection IV. Because it is broad, it is the default on all four armour pieces unless you have a specific threat in mind.
The four variants
- Protection — all damage types, the balanced default
- Fire Protection — fire and lava damage, plus shorter burn time
- Blast Protection — explosions and knockback, useful against creepers and TNT
- Projectile Protection — arrows and other projectiles, useful against skeletons and pillagers
Do not stack the same variant twice
Enchantment Protection Factor (EPF) has diminishing returns, so four pieces of Protection IV is far better than trying to max one slot. The standard is Protection IV on each piece; if you live in the nether, one piece of Fire Protection can replace one Protection without much loss.
Protection is not absolute
Even full Protection IV does not make you invincible — fall damage, void damage, starvation, drowning and the wither effect bypass much of it. Combine armour with the right consumables (golden apples, Fire Resistance, Slow Falling) for real safety.