Please explain augmenting for a newbie?

[Maskraider-3992]

The game guide briefly explains the Caldesann’s Despair recipe:
Mind the words “Ancient”, “Flawless Royal gem”, “Legendary Gem of Rank …”

https://us.diablo3.com/en/game/guide/items/kanais-cube#recipes

Augment Ancient or Primal Ancient Item

Caldesann’s Despair

Enchants an Ancient or Primal Ancient Legendary or Set item with additional attribute points.
The resulting attribute depends on the gem color used.
Using this recipe with
3 Flawless Royal Rubies will augment an item with Strength,
3 Flawless Royal Topazes will add Intelligence,
3 Flawless Royal Emeralds will add Dexterity, and
3 Flawless Royal Amethysts will add Vitality.

To augment an Ancient or Primal Ancient weapon, a Legendary Gem of Rank 30 or higher is required. Augmenting an Ancient or Primal Ancient Ring or Amulet requires a Legendary Gem of Rank 40 or higher, while augmenting an Ancient or Primal Ancient piece of armor requires a Legendary Gem of Rank 50 or higher. The higher the rank of the Legendary Gem used, the more attribute points will be added to your item.

I have further explanation here.