Genre Question ?

Being new to composing.. I have a few questions about genres of music.. and sub-genres. I know the obvious ones.. like what a piece from the "classical" genre sounds like, or the "romantic" genre, etc. But what exactly does "neo" mean ? Like "neo-romantic" for example. Also, what exactly makes a piece be placed in these sub-genres.. Also, what makes a piece "contemporary" .. ?

Something more or less like this:

Baroque:

http://www.youtube.com/watch?v=WQRB3befRMo

Baroque-> Classical

http://www.youtube.com/watch?v=lQpD-EXtvzg

Classical

http://www.youtube.com/watch?v=Zegl7_zMj_Q

Classical -> Romantic

http://www.youtube.com/watch?v=W9CYLAuKdtU

Romantic

http://www.youtube.com/watch?v=KhoYauWJh54

Neo- Romantic

http://www.youtube.com/watch?v=gcBg-tXn0fs

Neo-Romantic just before everybody started doing his own style :P

http://www.youtube.com/watch?v=URKGIa0b_jI

XX Century

http://www.youtube.com/watch?v=hlR9rDJMEiQ

XX Century

http://www.youtube.com/watch?v=LnuN_TORtC4

XX Century

http://www.youtube.com/watch?v=C68SkzGb6Ww

XX Century

http://www.youtube.com/watch?v=jwA8xKAIfbg

XX Century

http://www.youtube.com/watch?v=EoDhmR5eZr0

XX Century

http://www.youtube.com/watch?v=pF-F6-VFCWM

XX Century

http://www.youtube.com/watch?v=ePBB-NO8vKg

It gets more and more complex in harmony, rhythm, colors, form, development, every single aspect of music.

EDIT:

Oh, "Contemporary" suppose to be what composers are writing right now... but in style, not in dates, I could write a baroque piece in year 2013 and it won't be contemporary, some composers live in a period of time but write in another, older or newer.