Tolkien's Middle Earth is one of the richest fantasy worlds ever conceived; so rich that few are familiar with the entire mythos. The Silmarillion describes the history before The Lord of the Rings, and acts as an encyclopedic record of how the world of Arda came to be.
As it turns out, there are a lot of things that happened before The Hobbit. Tolkien's most well-known tales — those that have been brought to the screen — stick to covering events from the Third Age, and only allude to the millennia of lore that lead up to the destruction of the One Ring.
Some of the greatest characters Tolkien created aren't that well known. The general lack of knowledge regarding the extended LoTR universe has spawned some incorrect fan theories, and has left a lot of room for confusion among casual fans, even those who have read The Lord of the Rings.
Here are the most important things to know to understand The Lord of the Rings, the creation of the world known as Arda, and all the magical creatures that inhabit it.
Though it's tempting to call the world of LoTR Middle Earth, that name only refers to the continent where the events of the books take place. The world as a whole is called Arda, and consists of two main continents, Middle Earth and Aman.
Then there are the seas: Ekkaia, or the Encircling Sea, is the "mighty ocean" that surrounds the continents; Belegaer, the Great Sea, separates the two continents from one another, with Aman in the west and Middle Earth in the east. This world exists in the universe known as Eä, created by Eru Ilúvatar.
Eru Ilúvatar is Arda's equivalent to God. He was the first being to exist in an infinite sea of nothingness, and so he made the universe, Eä, and other beings to be his companions. He created the Ainur, which are essentially angels, and those are divided into two groups: the Valar, and their servants, the Maiar (the singular of which is Maia).
There were 15 Valar in total, but four are especially important for the purposes of understanding the events in The Hobbit and LoTR. These four are Manwë, Aulë, Yavanna, and Melkor, who in turn fashioned their own servants, the Maiar. The Valar assisted Eru in creating the world Arda, literally singing it into life, but one sang a discordant harmony.
Manwë was the king of the Valar, sometimes called the Wind King, as he lived atop the tallest mountain in the world, Mount Taniquetil in Valinor (the realm of the Valar on Aman).
He was the first Ainur, and is considered to be the brother of the evil Melkor. Manwë was appointed ruler of Arda when it was formed, earning him his most frequently used title, the Elder King.
To do his part in thwarting his evil brother, Manwë created the Great Eagles, led by their king, Thorondor. The Great Eagles were integral to the fight against evil, and became the greatest foes of Melkor (or Morgoth) and his lieutenant, Sauron.
Yavanna was the Queen of the Earth, Giver of Fruits, and wife of Aulë. She brought forth life on Arda in a place known as the Spring of Arda, but the life she created was soon blighted when Melkor released his poisons into the world.
Melkor had also destroyed the Two Lamps, the world's only sources of light, so Yavanna sang into existence the Two Trees: Laurelin (the Gold Tree) and Telperion (the Silver Tree). The trees gave light to Aman, but Middle Earth remained in darkness.
In response to the darkening of Middle Earth, Yavanna put all the living things of that continent into a great sleep, and they would not be awoken until the forging of the sun and moon. Fearing the material greed of other beings, namely the dwarves, she begged Eru to help create guardians to defend her plant life, and so the Ents (those giant tree people) were created.