1) End; created by the Moirai, not intended to actually be used

2) Overworld; created by a combination of Notch's, Herobrine's, and Steve's efforts

3) Aether; created by Notch as a place for the dead to rest for eternity and for the gods to retreat to and relax

4) Nether; created by Herobrine to be his own personal resting place, later to be used as hell and punishment for dark souls