p stands for
parameter, these “names” are used, when it isn’t clear what the value there is.
TASK_CHAT_TO_PED(Ped ped, Ped target, Any p2, float p3, float p4, float p5, float p6, float p7)
the first two parameter are already determined as
Ped target these are pretty much self-explaining.
p2 seems to be a flag or so, this probably changes what happens when calling the native.
p3, p4, p5, p6 & p7 are always
0f (would be
0.0 in lua) so it is hard to tell what these are, that is why they are still called
p3, p4, p5, p6 & p7
Some natives have description which give an insight in what these parameters could be or how to use them.
p2 tend to be 16, 17 or 1 p3 to p7 tend to be 0.0
So you could just try to use the native the same way rockstar did in their scripts.
I hope this little explanation helps you