Let me give you an introduction for this two.

Enchantment:

An item can be enchanted up to 4 times, meaning up to 4 options. Enhanced item cannot be enchanted,Armor can be enchanted up to 2 times, and accessories may not be enchanted,when an enchantment fails, only the item is recovered while the gem and charm of luck (if used) is lost.

* Warning *
   Item cannot be enchanted if has been enhanced.
- If you succeed in enchanting
  option that was on the enchanting stone will get transferred onto the item
- If you fail in enchanting
  item will remain, but stones and charms will disappear

In here i won't teach you combination of stones or emerald :)

Enhancement:

When you fail an enhancement, you will lose the item and everything used in the attempt. Please keep this in mind and think carefully before making enhancement attempts.

If you succeed in enhancing
  Weapons increase by 6 and armors increase by 3
- If you fail in enhancing
  Everything put into enhancing disappears. Even the dreams and hopes.
- Nothing more about enhancement!
  People usually think that enhancement is up to level 5, but it can be done up to level 10.However, success rate get quite low from level 6.

Tips for enhancement:

As the 1st and 2nd of enhancement of weopons or armour will be 100% succesful so you do not have to use the sapphire charm.As for 3rd of enhancement although the success rate drop there will be no need of charms too in my opinion,but when it 4th please use the sapphire charm.Note that the lost of your items ,i will not be responsible for that ;P

What is the difference between the Added Damage and Increased Attack Power?
 
It means increased Attack will affects the damage in all [Abilities/Skills/Rage] related attacks whereas Added damage only adds damage to the normal attack that character deals on the target.

However, because increased Attack Power ranges from 1-15 whereas Added Damage 1-20, the choice is up to the users.

What are Sapphire Charm?

Sapphire charm is a charm that protects the weapon and its options from being destroyed when you fail the enhancement.

However, because essence is different from enchantments or enhancements, so it does not get saved even if you use the Sapphire Charm.

What are essence?

Essence stones are stones that have special ability and make your weopon glows :).There will be status effect too ;).You can use the charm of essence removal to remove essence from your weopon or armour.