Just to all you fallout knowledgeable people. I'm trying to understand some of the faction in the fallout world.

OK let me see if I got this right, The enclave are the old US government and some of its army. The BOS are some of the US army also. So who are the NCR exactly? Are they parts of the old Californian army?

Why do the enclave have so much advanced pre-war tech? Also are there still a lot of American states that have not been explored? Is it possible that there are still many factions to be found?

I only started playing from fallout 3 and I have to say the games lore and game in general is great! I also think NV is great to.

BOS are descended from the army at one specific military base.

NCR have no connections to old world military or politics.

The Enclave have lots of advanced pre-war tech because they were most prepared for what happened.

The wiki should have most of the information you want in detail.

If you think FO3's lore is great you should really play FO1 and FO2.
I'm sure you'll be turned off by it's ancient graphics but the lore there is like 10 times that of FO3.

Not to mention they, oddly, WANTED a Nuclear War to happen.

Edit: Plus, prior to the war, the Enclave was essentially a shadow government. (I was aiming this edit to the OP by the way)

So they were responsible for the development of a lot of technology?

Why does the NCR not have much tech? and has the enclave been pretty much wiped out?

Because the NCR was founded somewhere between Fallout and Fallout 2 from a village called Shady Sands, imagine them as the 'Frontier America' of Post War America. and The Enclave is advanced because, as mentioned earlier, they were PREPARED, they essentially wanted this to happen. While the world suffered around them, The Enclave was just as the name states, an inward group. They continued designing power armor, making weapons, and all of the fancy retro-futuristic sci-fi esque tech we see.

Aye, plus from what I remember they were made up of disparite people from goverment, official agencies, big US corporations and suchlike.

Ah thats clears a lot up, when I get time I will read the wiki. Thanks guys!

Oh also are the enclave pretty much gone now? after broken steel is there really anyway for them to come back?

The Enclave was annihilated with the destrcution of their main base in Fallout 2. Then they were annihilated with the destruction of both of their main bases in Fallout 3 and the Broken Steel DLC.

Just think of them as post-apocalyptic herpes- no matter how many times you get rid of it, it keeps coming back but it's ineffectual and doesn't really do much besides create a nuisance before fading away again.