The Fellowship of the Ring had nine members. The group was deliberately formed as the Nine Walkers, matching and opposing Sauron’s nine Ringwraiths, also known as the Nazgûl.
The company represented several peoples of Middle-earth: Frodo Baggins, Samwise Gamgee, Merry Brandybuck and Pippin Took were Hobbits; Aragorn and Boromir were Men; Legolas was an Elf; Gimli was a Dwarf; and Gandalf was a Maia appearing in the role of a Wizard.
The number nine does not mean that every ally travelling with the Fellowship counted as a formal member. Elrond, Bilbo, and the residents of Rivendell supported the quest, while other characters joined or aided members later. The Fellowship also did not remain together for the entire journey: it broke at Amon Hen, after which its members continued the mission in separate groups. The title can refer both to the company itself and to the first volume of Tolkien’s trilogy.