If you've got a Nexus 5 and are wondering what the differences are, I've got a table of those differences (as far as I can find) here:
http://forums.androidcentral.com/google-nexus-5/588066-differences-between-american-models-nexus-5-nexus-5x.html
http://forums.androidcentral.com/google-nexus-5/588066-differences-between-american-models-nexus-5-nexus-5x.html