clips are what hold the rounds in place, wether inside or outside the magazine.

for example, on M1's there are what are called stripper clips, its a strip of metal that holds 5 rounds together for easy reloading.

a magazine is an actual "ammo box" it has a casing for storing, loading ammo.

technically, all magazines have clips as the clips is what holds the ammo solidly in a magazine

clip:



magazine: