I have often used those three terms almost interchangeably, yes, even computer scientist. After all, most of us have a degree in computer science, so what does that make us? However, recently I find that those three things have come to take on more and more distinct personalities in my mind. [...] It is difficult to define what each one should be, (it is more of a gut feel rather than a strict delineation) they are very similar (and rightly so), but I am going to attempt to do it anyway.

He splits them up according to a few criteria - how their code looks, how it works and what level their math skills are at. The photos he uses to further define each are pretty dead on too.