LOTR CHARACTERS PAGE #1
Weapon(s): Sword: Glamdring and staff
Gandalf is almost as old as the Third Age itself. He is a Maia spirit which means he is immortal. He was sent to Middle-Earth from Valinor, the Undying Lands to guide the residents there. Cirdain of the Grey Havens gave Gandalf Narya The Great, Ring of Fire, one of the Three Rings given to the Elves. Gandalf the Grey was second in the order of Istari only to Saruman, who, being "the White", possessed the most power. However, when the Valar sent Gandalf back to Middle-Earth as Gandalf the White, his powers could then overpower Saruman, because of Saruman's conversion to Sauron's power, he lost most of his Istari power. But the Third Age was Gandalf's Age to serve Middle-Earth and when the years of the King came to pass, he was required to return to Valinor with the last of the Elves and the Ring Bearers.
As for how Gandalf came across Glamdring, that is a story that is found
in The Hobbit. After, helping turn trolls into stone, Gandalf, the Dwarves,
and Bilbo entered the troll's cave. Gandalf took a sword, that would soon be
identified as Glamdring, whom Turgeon, King of Gondolin weilded in the First
Age. In the same cave, Bilbo found his sword Sting, that was also made in Gondolin
in the First Age.
As far as Gandalf's magical power, the only thing we know for certain is that he is more powerful as Gandalf the White, than Gandalf the Grey. There seems to be no boundary to his power, but some of the specifics are a stone that can used as a light and some kind of pushing force that he used against Saruman. He also knows many spells.
Personnally, Gandalf is my favorite LOTR character. If you think about it, if it wasn't for him, Sauron would control Middle-Earth as we know it.