hi! i can help!
NU'EST is Pledis Entertainment's first boy group, debuted in 2012 with 5 members. They have a subunit, NU'EST W, which was active while Minhyun was in Wanna One. There was also NU'EST M, which promoted in China with Jason (Fu Longfei) but no one talks about that lol. The
kprofiles page on them has more info about the members, like their positions and such.
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When I first started getting into NU'EST I found this fanmade documentary very helpful:
This version was published late last year, so it doesn't include the release of WAKE,N, Happily Ever After, or the other things that have happened this year.
I actually first saw the older version, which was made before Produce 101 season 2 aired. At any rate, this'll get you caught up on the history of NU'EST and
this playlist by the same person also includes videos for each member.
As for songs, you could watch this (admittedly long) live stage compilation of NU'EST performing for MBC. It'll give you a good sampling of title tracks and b-sides from their debut FACE to BET BET, including NU'EST W. What's missing there is I'm Bad, which was a special anniversary single that they didn't promote, and NU'EST W's Where You At. They also have a Japanese discography.
I hope this helps! If you have any questions you can ask me. I'm not the oldest L.O.Λ.E, but I'll do my best!