Enchantments are permanent stat bonuses fused onto a specific piece of gear. There are 19 of them, they are bought only with Glory from the Arena Shop, and they are the main reason a competitive player cares about arena rating at all.
The 19 enchantments span the same five rarity tiers as gear, and the tier sets both the Glory price and the size of the bonus. Each is deliberately sized at roughly one rarity tier's worth of stats, so an enchantment is a meaningful upgrade without replacing the value of the gear underneath it.
A sample of what they do:
Buying an enchantment puts it in your inventory; it is not applied at purchase. You then choose a gear piece and fuse it on. A piece of gear carries at most ONE enchantment at a time, so the choice of which piece to enchant is as important as which enchantment to buy.
Applying one to a piece that already carries an enchantment REPLACES it, and the replaced enchantment is destroyed. There is no refund and it does not return to your inventory. The game asks you to confirm, naming what will be lost, precisely because a mistaken tap here can throw away a top-tier enchantment that cost a season of Glory.
If you want an enchantment off a piece without putting a new one on, the Blacksmith will strip it for a gold fee that scales with its tier. That also does not refund the Glory: stripping is for freeing up a gear piece, not for recovering value.
An enchantment's stats are added to the gear piece and then treated like the item's own rolled stats. That has one consequence worth knowing: they share the item's gear-condition scaling, so an enchanted weapon at low condition delivers a reduced enchantment bonus too. Repairing gear protects the enchantment investment, not just the base item.
Because the enchantment lives on the ITEM, it travels with it. Selling or trading an enchanted piece hands the enchantment to the buyer, which is why gear listed on the marketplace cannot be enchanted while it waits: otherwise a seller could list at an unenchanted price and then quietly add value the buyer paid nothing for.