A smidgen is a little bit of something. If you're only hungry enough for a little bit of ice cream, you might ask for just a smidgen in your bowl.
Maybe you prefer just a smidgen of ketchup on your fries, or you might speak a smidgen of German, enough to buy your train tickets in Berlin. You can use the adjective smidgen to talk about a tad of anything, although it's often used for describing or requesting little bits of food. It's thought to have come from the Scottish word smitch, "a small amount or an insignificant person."