This may be a basic question, but it's something I'm having a hard time understanding. The Wikipedia article I am reading about spin http://en.wikipedia.org/wiki/Particle_spin seems to be saying that spin isn't really what we think of on the macroscopic scale (ie: spinning on an axis like a planet). So my question is, what exactly IS spin, and how is it measured? Any help in understanding this would be great. Thank you all.