USB sticks are really portable storage - you copy your artwork to one from a computer, give the stick to your card printer & they can make the cards using the artwork you stored on the stick.


Phones also can act as portable storage, like a USB stick, if you connect them to a computer with a USB cable.


Notice that the plug on the ends of the USB stick & the cable where it goes to the computer are the same, whereas the plug on other end of the cable going the phone is much smaller - the USB socket on your phone is designed to be used with that cable, rather than to connect a USB stick to.