SATA is the fast new standard in computer bus technology (the bus refers to parts of the system that transfer data). So while you may want a SATA hard drive or optical drive, many PCs on the market still have power supplies that do not conain any or enough power cables to support SATA devices (they use a different kind of power plug than the older devices). You can easily add this cable adapter to your one of your computer's Molex connectors and be able to provide power for up to 2 SATA drives.