eSATA stands for External Serial Advanced Technology Attachment and is a bus interface for connecting external storage devices. It was developed to bring the full bandwidth and speed of internal SATA drives to external enclosures, bypassing the protocol conversion bottlenecks that plagued early USB and FireWire connections. Physically, the eSATA connector differs slightly from the internal SATA connector; it lacks the L-shaped key to prevent internal unshielded cables from being used externally and features a more robust design for frequent insertion cycles. One significant limitation of the standard eSATA specification is that it does not transmit electricity, meaning external drives usually require their own separate power supply, unlike many bus-powered USB devices which carry both data and power in a single cable.