Resurrected.
The reason why Minato came out after Naruto episode 660 is that Orochimaru and Sasuke went to the basement of the Uchiha clan in Konoha Village. In order to learn the truth, they gave sacrifices to the ghouls and then resurrected Minato.
"Naruto" is adapted from the comic of the same name by Japanese cartoonist Masashi Kishimoto. It premiered on October 3, 2002 in all 6 series of TV Tokyo and Gifu Broadcasting, with 220 episodes.