For info on Mai’s first augment, see Demonic Eye of the Sable Waif.
Abilities are Active Skills.
Augments are Passive Skills.
“Abilities and Augments, together commonly referred to as your “Skills.” Slightly different from spells, Abilities do exactly what they prescribe without being able to be modified. They can cost mana to use or have a cooldown period before they can be used again. Augments are the passive or toggleable versions of abilities, constantly being active. Each Augment takes away from your total mana regeneration rate, even when not in use. You can have a total of seven Abilities and seven Augments, but acquiring them is slightly different. They are only unlocked through raising your level, your class level, or the corresponding stat requirements. Many require a combination, and once unlocked, they must also be purchased with points.” Selene ch.5
“Abilities and Augments, have levels of their own that increase through use. Their max level is limited by either your level, or your class level” Selene ch.5
Skills can evolve into stronger versions or sync up to create new ones at class evolutions.