What is the difference between the $"$p$-3"$ and $"$m$-3"$ utility classes in Bootstrap?

Question $2$ options:

$1)$

The $"$p$-3"$ class adds $3$ pixels of padding to an element, while the $"$m$-3"$ class adds $3$ pixels of margin to an element

$2)$

The $"$p$-3"$ class adds $3$ units of padding to an element, while the $"$m$-3"$ class adds $3$ units of margin to an element

$3)$

The $"$p$-3"$ class adds $3$ units of padding to all sides of an element, while the $"$m$-3"$ class adds $3$ units of margin to all sides of an element