My understanding:
A magazine is
the box
that holds the rounds in the gun
which could be detached or not and
is always in while you shoot.
A clip is
the clip
that holds the rounds in the gun
which is always detached but
is always in while you shoot.
Nope.
Some clips stay in the gun (en-bloc clips, moon clips), most do not (stripper clips). The difference between a clip and a magazine is that a magazine has some mechanism to feed the ammunition to the firearm; a clip merely holds ammunition while:
A) In a cylinder (moon clips)
B) In an internal magazine (en-bloc clips) or
C) Loading a magazine (stripper clips)
If you can't understand the difference there really isn't any hope for you.
...so the name for
a distinct container of ammunition, where you don't give a damn whether it's a box or not because it has no bearing on the logistical matters you are actually concerned with
that holds the rounds in the gun
which is always detached but
is always in while you shoot
...is...?
Could be either a clip or a mag, but importantly it's distinctly one or the other. The terms aren't interchangeable.
Or you could be loading individual rounds/shells into the gun, like with the lever action rifle or the pump shotgun.