We already know this letter:
which is pronounced pretty much the way we pronounce the letter p.
There’s some air behind it, but not much. It’s
romanized as p or b, depending upon its sound..
This letter,
has an extra-strength puff of
air behind it. It’s always romanized as p.
In older versions of Korean romanization, this letter
was romanized as p’; now it’s just
p. This is why you really have to learn the alphabet, and cannot
rely on Romanization. If you see the letter
p in a Romanized word, you can’t tell if you
have a
or
a
.
And this letter,
has no air;
it's the p of spin.
Your throat sort of tightens up when you say it; the technical term for this is
that the letter
is
glottalized. It is
romanized as pp.