The Wireless SD card shield allows an Arduino board to communicate wirelessly using a wireless module, and adds storage to your Arduino project. The XBee Shield is based on the Xbee modules from Digi, but can use any Bee module with the same footprint. It supports SD, SDHC, or MicroSD TF cards. Use the on-board toggle switch to select the SD card type. And when you want plug a sd card on it,you should select the switch to the right direction.
About the wireless module, it only uses you two pins from PD0 to PD7. With two jump wire, you can select the wireless module to communicate with USB-to-serial converter or with the microcontroller.
It just uses the SPI ports of Arduino to transfer data with SD , and you can plug more other shield on it.