It's sort of like...not the smallest unit, but a small unit for measuring digital storage.

这有点像是......不是最小的单位，应该是用于描述数位储存的小单位。

A " memory card" is a small, flat piece of typically plastic and metal that you put into something like a digital camera, that provides additional digital storage – a place where you can put more digital information, such as a digital photograph.

“存储卡”是一种通常由塑料和金属制成的小而扁平的部件，您可以将其放入数码相机之类的东西中，它提供额外的数字存储——您可以在其中放置更多数字信息（例如数码照片）的地方。