The card reader is a USB device which can be used to read the removable memory card (usually SD type these days) which stores pics on the camera.
Note that most cameras also have a small amount of internal storage (say 4 or 5 pictures worth) which can only be accessed via a cable or dock attached to the camera. If you are having problems accessing pictures on the camera avoid using the internal memory (just remove the memory card and fire off some test shots to fill the internal memory -- then any subsequent shots will be stored on the card).
However, I still would like to send my pics via email to my family and friends. If my USB device is indeed defective, is it possible to buy another one and see if that works? I have used it before to download my pictures and I have had no problems until recently.