Minecraft wiki entry for Combat, associated text: Fire Protection is very effective in the Nether, since you have many fire-related things to worry about; blaze fireballs, ghast explosions, fire everywhere, and lava pouring from the walls and ceilings. It can also be considered as an Anti-Fire Aspect (Flame) enchantment, since if the foe relies on fire to deal damage, Fire Protection can give you a great advantage.
Protection in its raw form gives you moderate protection from most kinds of damage. It is recommended to use this enchantment with diamond or netherite armor, since diamond armor combined with a high Protection level gives you an overall great defense, plus damage taken from Protection-enchanted armor instantly goes to your armor durability. Diamond armor has relatively high durability, making it the best choice for this, upgrading it to netherite armor gives you Knockback resistance.
Projectile Protection is useful when fighting skeletons or pillagers as they rely on arrows to deal damage and this enchantment can block most of that damage. Projectile Protection is also recommended if your bow is low on durability. This means that you will need to go into close combat to strike, and foes will often take advantage of this by striking you from afar. This enchantment, especially Projectile Protection IV, is also useful against drowned holding a trident. It decreases heavy amounts of damage from thrown trident impact.
Blast Protection is very good against creepers and ghasts, as their only form of attack is an explosion, which Blast Protection is effective against. It is useful when fighting with, near or around TNT (such like minefields) as it reduces damage taken from those sources. It is also efficient for the non-combat related topic of TNT mining.
Feather Falling is good if you are in a high place, as this enchantment protects against damage from falling. It can successfully protect against the form of combat known as "Knockback striking" if the only environmental damage is fall damage. It is also very valuable if you frequently use ender pearls or when you fall while using elytra.
Respiration is not very combat-related, as you will rarely be fighting underwater (except if you live in an ocean). However, should someone drop sand above you then it can increase your survivability of the attack, due to respiration giving you more time to breathe underwater. This enchantment is also useful when fighting against drowned.
Depth Strider is good if you are raiding an ocean monument, because it allows you to move faster underwater and avoid guardians more easily.