What is planet Ahch-To in Star Wars?

Planet: Ahch To

 Warning some Spoilers from Star Wars: The Force Awakens.

Planet that is thought to be home to the first Jedi Temple.  This planet is sought out and used as a refuge by Jedi Master Luke Skywalker. 

Population:  Unknown (At least one Luke Skywalker)

Environment: Ocean / Islands

Cities: Unknown

Animals, Fauna - Appears to be a lush ocean environment that included birds and moss.

Lore:

Ahch-To is thought to be home of the first Jedi Temple.  It was sought out by Jedi Master Luke Skywalker after his Jedi trainees were killed by the Knights of Ren. 

Working for the Resistance, Rey pieces together two parts of a map and flies the Millennnium Falcon to the planet.  Rey is accompanied by Chewbaca and R2-DC.  There she locates Luke Skywalker on the planet.

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