Statement of Purpose is something required by all schools, and where you talk about academic background/research experience/why you like that school etc.
Personal statement (which is required by the UCs and some other places like Michigan) will have a prompt like "explain how your personal background influenced your decision to pursue graduate studies...". I mostly put some BS, kinda similar to my college application essays.
I may be wrong, but I'm under the impression that for physics students, the personal statement can make a difference only if you are from a very non-traditional background and/or you're being considered for diversity fellowships.
From what I recall, most schools pick either one or the other (i.e. SOP or PS) and then use that word to mean "The essay in which you describe your academic and research qualifications". I know this because on roughly 3-4 of my applications, I had to re-compile my Statement of Purpose to have the word Personal Statement in it instead. However, in the instance that a school makes a distinction between the two and asks for both, I've found that the way you've identified them is typically how they do it.