Who are they and what do they wear? also Are they against the Brotherhood of Steel?
they are a group that is dedicated to rebuilding society. there capital city has a population over 20,000 and growing. although there intentions are good they have been known to take part in shady dealings to further there cause. as for there armor they probably wear combat armor and military uniforms.
the N.C.R rangers are special forces designed for advanced operations. they were the armor that the "Badass from the teaser" wears. you know with the gas mask.
there army is extremely large. the largest in the entire country. they are extremely influential and powerful(on par with the enclave) except they believe in human rights and democracy