The 2.5-inch form factor was and is a common standard for laptop hard drives. For compatibility reasons, the format is also used for SSDs. Some 2.5-inch drives may use the SAS (Serial Attached SCSI) interface in servers, but SATA is the standard interface for nearly all other use cases.
SATA is short for Serial-ATA, which in turn is short for Serial Advanced Technology Attachment. This computer bus interface was originally designed for traditional hard drives.
Although it is considerably faster than its predecessor Parallel ATA, it will effectively cap the speeds of modern, high-end SSDs. Modern motherboards usually come with PCIe M.2 slots, which greatly improve theoretical transfer rates. The common SATA revision 3.0 (or SATA 6 Gbps) with SATA offers a theoretical transfer rate of up to 6 Gb/s or 600 MB/s.