Gandalf is the wizard character created by J.R.R. Tolkien who leads the Fellowship.
Gandalf the Grey helps identify the danger posed by Bilbo’s ring and brings Frodo into the wider struggle against Sauron. At the Council of Elrond, he supports the plan to send the Ring toward Mordor, and he becomes the Fellowship’s principal guide during its early journey.
After defeating the Balrog on the Bridge of Khazad-dûm, Gandalf returns as Gandalf the White. This transformation marks a change in authority and mission, not the arrival of a completely different person. Saruman is another wizard, but he betrays the Free Peoples, while Radagast is associated especially with animals and the wild.