Grindelwald is a dark wizard like Voldemort. But their ideology is different. Grindelwald wanted wizards to conquer the muggles but Voldemort wanted pure bloods to conquer the others. Grindelwald was student of Dumstrang but he went out of his school. He thought he need the Deathly hollows to bring his ideology to real life. So he went to Godric's hollow because Ignotus Peverell died there. There was Dumbledore's family so Grindelwald and Dumbledore met. Long time ago, they had same Ideology 'For the Greater Good'. But after Ariana Dumbledore's death they split up.

Finally Grindelwald get the Elder wand from Gregorovitch. But after the duel with Dumbledore he lost and Dumbledore took the Elder wand. He spent rest of his life at Numengard until he killed by Voldemort's killing curse. It is funny that Numengard is the prison made by himself.

As I said, Grindelwald defeated by Dumbledore before he bring his ideology to real life.