Question concerning forces(F=MA) (F=PA)

Hi guys first time poster here I have what I think is a super simple question(s)

I'm an apprentice plumber and we often use the formula F=PA and it was brought up that F=MA as well and the instructor(being a plumber) mentioned that he's tried out the latter formula using 9.806m/s2 and it never ends up being the same the the former formula.

I've taken a look into the differences and haven't really found anything directly mentioning the two which leads me to think that they're just two separate things entirely but i'm not really too sure of myself, i'm a plumber not a physicist.

If someone could explain this to me in a way I could understand that would be really appreciated!