XD is XD-PICTURE CARD which means “Extreme Digital” from SDUSB.NET of memory card manufacturer.
Description:
*Capacity: 128MB/256MB/512MB/1GB/2GB/4GB/8GB/16GB/32GB
*Dimensions: 20mm*25mm*1.7mm
*Format: XD Picture Card
*High capacity and high speed transfers rate
*Small and compact for the most portable digital cameras
*Ultra-thin, ultra-small
*Interface: 22 pin