Tridents are one the most unusual weapons in Minecraft. They are not craftable or available in loot. They can only be obtained if you are lucky enough to see a drowned slain drop one. 15% of those who drown in Bedrock Edition (6.25 in Java Edition), spawn with a Trident, and there is an 8.5% chance that they will drop one.
Players can enchant the item once they get it. Tridents have exclusive access to enchantments that can only be used on tridents, except Mending I or any of the three levels in Unbreaking.
Loyalty can only be obtained by using a trident. This enchantment can be increased to level three, and this is where the difference lies.
You can use tridents as projectile weapons. Crafters can press the use button while holding a trident in one hand and prepare a throw. Then, they can release it when ready. However, they will need to retrieve the trident afterward. This can be frustrating.
This is where Loyalty enchantments are useful. A trident that has Loyalty will always be returned to the player's hand. If they die before the trident comes back, the item will drop. It can then despawn.
Loyalty II, III, and I all accomplish the same thing but in a different way. Loyalty I performs the slowest while Loyalty II is the fastest. Mojang and the Minecraft Wiki don't currently provide any information on the speed of each level, however the differences between I-III are significant.
In certain circumstances loyalty can be very beneficial. Equipment and elements that fall into the Void are permanently lost in the End. Players can still throw their trident at anything and it will end up in the void.
The loyalty enchantments will allow the trident to return after 15 blocks in void. This exclusive Bedrock Edition feature is not available to Java players.
You should also know that tridents cannot be used in dispensers and will not return once enchanted. The enchantment works only if the player throws their trident.
There are many ways to acquire loyalty I, II, or III. It is easiest to acquire loyalty I, II or III by using an enchantment table. The enchantments can be cycled until you find the one that suits your needs.
Librarian Minecraft villager can also trade books for money. These books can also be obtained through loot or fishing, but they are not random.