My computer doesn't have a port for a Memory Stick, so using any one of Sony's products that use them is impossible without using this adapter. Sony's digital cameras and digital voice recorders (why I have one) all use this media format, so forgetting to buy one can prevent your enjoyment of your own equipment.To use the adapter, you just slide the Stick into the adapter, and then the adapter goes into your regular 3.5" disk drive, looking just like a regular disk. There is some software included to assist in the applications you will use with it, inluding the voice recognition program I originally hoped to use, but is sold separately.I don't really know why the item is as much as it is, but it is necessary for most folks. I guess one way of looking at it is that it offers the same functionality as a Compact Flash card reader, just more expensive.