For those struggling with terminology, allow my experience of having a daughter to help:
Night-time: Dark outside
AnyPony: Any Player
Friend(s): Player's who contributed mana towards Nightmare Moon's ability cost.
Pegasi: Pegasus
Applejack, Fluttershy, Pinkie Pie, Rainbow Dash and Rarity: Creature cards for the five 'Friends of Eternia'.
Nightmare Moon: Goddess of Night
Princess Luna: Nightmare Moon before becoming evil.
Princess Twilight Sparkle: The lead character of My Little Pony, she trains to replace Princess Luna's vacant position.
That's "Equestria," Eternia is the he-man world.