Stands for "Serial Advanced Technology Attachment," or "Serial ATA."
SATA is a standard bus interface for connecting storage devices like hard drives, solid-state drives, and optical drives to a computer's motherboard. It replaced the previous standard, parallel ATA, and provides much faster transfer speeds using smaller and simpler cables.
The SATA standard has received several updates since its introduction in 2003. SATA 3, the third and most recent revision, supports a maximum data transfer speed of 6 Gbps (4.8 Gbps, or 600 MB/s, after accounting for data encoding overhead). The specification also allows the hot-swapping of devices so users can connect and disconnect drives without shutting down their computers.
Both SATA drives and parallel ATA drives are IDE devices, which means they integrate the storage controller chip into the drives themselves. This adds more physical size and complexity to the drives but simplifies the connection to the motherboard. SATA cables are significantly thinner than parallel ATA cables, making them easier to organize inside a computer's case. SATA devices each have their own independent bus, unlike parallel ATA devices that share a single bus between two devices (requiring two drives to share one cable, and for the drives to have primary and secondary roles assigned using jumpers).
NOTE: A variant of SATA, called eSATA, exists for external hard drive connections.