The Races in Middle earth:
The Ainur were angelic spirits created by Eru Ilúvatar at the Beginning. The Ainur who subsequently entered the physical world of Middle-earth were the Valar ("powers"), though that term came to refer primarily to the mightiest among them. Lesser spirits were called the Maiar. Most of the Valar and Maiar withdrew from Middle-earth to the Undying Lands of Valinor, though some of the Maiar, such as the Wizards or Istari, Melian, the Balrogs, and the Dark Lord Sauron, assumed mortal forms to help or hinder the peoples of Middle-earth.
The Free Peoples of Middle-earth were the four races that had never fallen under the sway of the evil spirits Morgoth or Sauron: Elves, Men, Dwarves and Ents. Strictly speaking, among Men it was only the Men of the West who were Free People, particularly the descendants of the Dúnedain of the Isle of Númenor, as most Men of the East and South of Middle-earth became servants of Morgoth and Sauron over the ages. The Ent Treebeard quotes lines from a traditional lay listing them.
First came the four, the free peoples
Eldest of all, the elf-children
Dwarf the delver, dark are his houses
Ent the earthborn, old as mountains
Man the mortal, master of horses
After encountering the hobbits Merry and Pippin, he consents that hobbits are a fifth free people, adding a fifth line, "Half-grown hobbits, the hole-dwellers".
Enslaved peoples were those races that had fallen under the sway of the evil spirits Morgoth and Sauron, also known by the Free Peoples as 'Servants of the Enemy'. They included Orcs, Trolls and Men. The origin of Orcs and Trolls is unclear, but they were races that were taken by Morgoth and corrupted through sorcery into their final evil nature and appearance. Men were rarely corrupted by Morgoth or Sauron in the same way. Rather, their hearts and minds were corrupted by power and evil impulses, while they retained the physical appearance of men. Prolonged service to Sauron however, did turn the bearers of the Rings of Power from Men into the wraith-like Nazgûl. Those men who were the servants of Morgoth or Sauron were mostly from the east and south of Middle-earth.
Tom Bombadil does not belong to any of the peoples of Middle-earth; Tolkien calls him the spirit of the countryside. Unlike the other races, he is seemingly unaffected by the One Ring and appears to predate the Children of Ilúvatar (Elves and Men). As to the nature of Bombadil, Tolkien himself said that some things should remain mysterious in any mythology, "especially if an explanation actually exists."
Tom is also known as "The First", "Master Tom", "Old Tom", "Iarwain Ben-adar" (a Sindarin name meaning "The Oldest without a father"). The Noldor call him "Orald" meaning "Very Old", Dwarves call him "Forn" (meaning: The Ancient).
Spirits of nature tied to rivers and waterways. Only two are mentioned by Tolkien: Goldberry, the wife of Tom Bombadil, and her mother the River-woman. It is unknown whether these beings were unique, part of a larger race, or a form of Maiar.
Giants other than Ents are referred to only a few times by Tolkien. Stone-giants of the Misty Mountains are said to lob stones at Thorin and Company in The Hobbit.
Dragons are already present in The Book of Lost Tales. Tolkien had been fascinated with dragons since childhood. As well as "dragon", Tolkien used the terms drake (from Old English draca, in turn from Latin draco and Greek δράκων), and worm (from Old English wyrm, "serpent", "dragon"). Tolkien named four dragons in his Middle-earth writings. Like the Old Norse dragon Fafnir, they are able to speak, and can be subtle of speech.