What is Necromancer?

I know that Sauron is meant but does Necromancer mean? Is it a race that Sauron belongs to or what does it mean?

It's someone who practices necromancy. Necromancy, according to Webster's is either:
1. the practice of devination by alledged communication with the dead
2. sorcery.

I'd say JRRT was going for the second sense here, but used the word "necromancer" to get the tie-in with death.

Anyway, if you want to know what Sauron was, he was a fallen Maia(Angel, if you like).

Necromancers are socrcers who specialize in summoning the dead and reanimating them. I don't know if Sauron actually did that, but he did some nasty stuff at Dol Guldur.

Sauron was a fallen Maia, an angelic being created before the world was. Originally a Maia of the Vala Aule(the Smith of the Valar), he was corrupted by Melkor(the first Dark Lord) in the distant past.

They are not nice people.

And if you read Terry Pratchett's book (the sequel to the Colour of Magic), someone asks, "What's neck romance?".

Remember, not everyone who reads Tolkien's Christian, and I'm sure Tolkien himself wouldn't like to hear the Maia called Angels, even if he created them as a parralel to that part of his beliefs.

Tolkien grew up in a time when seances and summoning spirits were all the rage in Europe and America from the 1870's onward, before it petered out in the 1930's (flash photography showed a lot of faking).

My guess is that Tolkien heard about seances and generally disapproved of them, eventually working them into his mythology.

Tolkien in fact called them Angels, niff. He said there are lots of Catholic influences in the Lord of the Rings. He associated the Valar with Angelic Gods, the Maiar-Angels, and the Istari-Guardian Angels.

I'm sorry if I offended anyone, but I wasn't asking anyone to believe in Angels, I'm just trying to give somone an idea of what Sauron was. Everyone knows Angels.

Sauron's necromancy did indeed involve working with spirits and phantoms. That kind of sorcery went all the way back to the First Age (such as when he caught Gorlim the Unhappy with his wife's phantom). And then there are the Ringwraiths.

And possibly the Barrow-wights, right? Whether or Elves or Men, assuming it wasn't solely the work of the Witch-King.

Grand Admiral Reese; you are right. Nasty people.

The word "Angel" just means messenger. Tolkien based the Valar on the gods of Classical Greece and Rome, but he was not a pagan and therefore they are not Powers in and of themselves, but extensions of the One. They were thus "angels," like all the other Ainur, and yet because they inhabited the world and became alligned with various natural forces, they are also "gods" (with a small G) who are still beholden to God (Eru).

I had not thought of the actual meaning of Angel, only the sense. Those are some good points. But I'm not sure he based his Valar on the gods of ancient Greece and Rome. Maybe he borrowed a few ideas, but they are drastically different, to my eyes.

And many like Tulkas and Orome are much more similar to Norse gods than greek ones.

You're right, I made my associations based on the pantheon I was most familiar with. When I read the Sil I didn't know much about Norse gods.