Equestria is the universe of the My Little Pony: Friendship is Magic. It is home to all kinds of creatures: ponies, dragons, griffons and many others.
The B Team Storyline
Equestria is where where Bender and the Crew usually went for their missions when villains (Especially Discord) scheme plans for the universe.
It is also the primary target of the League of Darkness which do not know where it is until the League gets their hands on someone who may know where it is. It was also a place for the Children of BlackGarurumon to go after as well. Equestria was eventually destroyed by the heroes who had to insure the Niburu entity didn't destroy and they had to choose a place and Equestria was the place since so many villains have been after it.
LOTM: The Angels Return
Their seeking power from the Primes has lead Angewomon and Myotismon, along with their friends, to Equestria. The Mane Six have taken a liking to their being here, and Mervamon has found Ponydramon.