What does it mean a skill is "upgraded"?

[Fanta]

The description of some weapon mentions "upgraded skills". E.g. Ballaro Level 10 says that using an upgraded skill gives 1 AP to every other ally.
What does it mean that a skill is upgraded? How do you upgrade it?

[Meewec]

i've assumed it means using a skill on that matches the place you are on his wheel. they get bonuses for that.

[Crimsomrider]

An Upgraded Skill is when a skill meets its requirement to trigger a stronger version of itself. If it meets its requirements the ability will have its name highlighted in gold with a sparkling effect next to it.

For example;

• For Lune it's when her abilities are able to consume stains
  
• For Monoco it's using specific abilities depending on his current spot on the mask-wheel (Agile abilities with Agile mask, Heavy abilities with Heavy mask etc...)
  
• For Sciel it's when her Dark abilities consume Foretell
  
• For Verso it's when he reaches a certain rank depending on the ability
  
• For Maelle it's when she's in the correct stance depending on the ability