A clip is not a magazine. It has no spring and does not feed the gun on its own. There are two main kinds.
Stripper clips
A strip of metal that holds rounds by the rim. Place it in a guide and push the rounds straight down into the magazine. The SKS, the Mauser and AR15 magazines with a loading guide all use them. Ammo often comes on stripper clips in cloth bandoleers.
En bloc clips
The clip goes into the gun with the rounds and is ejected when empty. The M1 Garand and its famous ping are the best-known example.