A Formspring question! Yay! (This one's not from Formspring itself :D) I edited it slightly by removing a part of it just because the public doesn't need to know that.
What's the difference between the terms pathan and pashtun? My dad's side of the family is pathan, but they moved to India a long long time ago and then from there to Pakistan. Can I be cool too and call myself pashtun?
Of course you can be cool like me and call yourself Pashtun :D Even if you have less than .00001% Pashtun blood in you, you can call yourself that.
To answer your first question:
Pashtun = Pakhtun = Pukhtun = Pushtun = Afghan. (The term "Afghan" today, however, is more synonymous with someone from Afghanistan, or a citizen of Afghanistan, whether Pashtun or non-Pashtun (e.g., Hazara, Tajik, Uzbek). So, a lotta Pashtuns from Pakistan don't like being called Afghans, especially if they don't support the idea of Pashtuns' independence from Pakistan.) On every Pashtun site you ever visit, you'll see lotsa debates on the term Pashtun and Pathan because many Pashtuns in Pakistan (and often in India) don't have a problem referring to themselves as Pathan.
The difference, however, is that "Pathan" is a term imposed on Pashtuns by outsiders/invaders, and many Pashtuns argue that it's not their original name and is therefore not authentic. It's also often used as a derogatory term against Pashtuns in Pakistan, so I'm personally not a fan of it either. So, just to make sure you don't anger any Pashtuns, calling them Pashtuns instead of Pathans might be the safer thing to do ;)