Serial ATA (Advanced Technology Attachment) is designed to transfer data between disks drives (hard and optical) and computer hardware and is the successor of ATA. SATA adapters and devices communicate over a high-speed serial link originally specified in SATA I at 1.5 Gb/s, then SATA 2 at 3 Gb/s, SATA 3 at 6 Gb/s, and the latest SATA 3.2 offers a transport speed of 16 Gb/s.
The serial interface means the connector is smaller (than ATA) and can run faster, because fast parallel data starts to suffer from skewing with some channels of the parallel connection being faster/slower than others. Serial data cannot skew. SATA does not just serialize ATA. For example, SATA 2 added native command queueing, originally a feature of SCSI, that allows handling multiple pending transactions rather than just one at a time. Also disk drives can organize the transactions and so offer faster operation.