Enchants are single use items that can be purchased or created using crafting. They can be used to enchant weapons and companions, allowing you to elemental attacks with your physical attack, by using the corresponding Plus stat. If you have a 20 FIR+ with an Enchanted weapon with ≤10 Fire, 10 extra damage will be Fire on top of your normal physical. Enchants have an only allowed maximum damage they can provide. Keep in mind that monsters can resist your elemental enchant in their own stats.