-
Parallel: I different version of the base card. For example, silver, refractor, blue wave, green scope, etc. You could say a parallel is a variation of the base card.
Insert: A sub-set of the base set. Will look totally different from the base card of that player.
Variation: Most commonly an image variation. Sometime can be hard to tell unless you know the set well. Panini will mark the back with a “V” sometimes to indicate its a variation.