eSATA is an interface for external SATA devices, mostly external hard drives. eSATA reaches transfer speeds 3X that of USB 2.0 and Firewire 400, and is a direct data interface to the computer, compared to the translation bottlenecks that occurs with USB and Firewire technologies. You do need a eSATA connection on your PC to connect a eSATA device, or an add-on card can be installed to your computer.