There are seven Lords of the Valar. They are
all sort of important, so unfortunately they must all be listed here. Manwë,
Ulmo, Aulë, Oromë, Mandos, Lórien and Tulkas. There
are also seven Queens, or Valier: Varda, Yavanna, Nienna, Estë, Vairë,
Vána and Nessa. Melkor used to be a Vala, but he doesn't count
any more. He and Manwë are brothers.
Manwë is lord of the air, and is Eru's favourite. He likes birds.
He's married to Varda, the lady of the stars. She is the favourite
of the Elves; in Sindarin they call her Elbereth and/or Gilthoniel, as found
in Lord of the Rings.
Ulmo is the lord of water, and is not married. He is scary but nice
and is fond of Elves and men. Ulmo is second in strength to Manwë.
Behind Ulmo in the strength contest is Aulë, who likes mining
and forging and all that. Aulë is married to Yavanna, who grows
plants and looks after animals.
Then there are Námo and Irmo, the lords of spirits, who are usually
just called (respectively) Mandos and Lórien after the places they
live. They are brothers. Mandos is older and looks after the
spirits of dead Elves in his halls. Lórien does things with
dreams and visions and all that. Mandos is married to Vairë the
weaver, who weaves the tapestries of history, and Lórien is with Estë,
who is a healer.
Nienna, who is either the sister of Manwë and Melkor or Mandos and
Lórien depending on which book you read, lives alone and is always
sorrowful. She grives for the marring of the world. Also, she's
responsible for dealing with the souls of departed Men.
Tulkas is physically strongest. He's into wrestling, and came last
to Arda to help fight Melkor. His wife is Nessa, sister of Oromë,
who likes deer and dancing. Oromë is less strong than Tulkas,
and also less jolly. He likes hunting. Oromë is married
to Vána, younger sister of Yavanna. Vána is good with
flowers and birds.
Now, I know you're probably going to forget most of these names. But the important ones to remember for now are Manwė, Varda, Mandos, Oromė, and Aulė. Everyone else can just be referred to as "that one there".
The word "Valar" is plural- the singular is "Vala", or "Valië" for the
females.