USB 1.1, or legacy USB, can support a data transfer rate of up to 12 megabits per second. USB 1.1 is found typically in computers developed before 2001. Most USB 2.0 devices can use a USB 1.1 port, but they will be limited to a 12 megabit per second transfer speed.
USB 2.0 provides transfer speeds up to 480 megabits per second. This allows for high-speed transfers with external hard drives. USB 1.1 devices can be used in a USB 2.0 port, but they will be able only to transfer at speeds of 12 megabits per second.
Serial Advanced Technology Attachment (SATA) allows data transfers at up to 6 gigabits per second, roughly 12 times the speed of USB 2.0. SATA is used for internal hard drives and disc drives. Note that most devices cannot reach SATA's maximum data transfer speed.
eSATA, or external SATA, is a variation on a standard SATA port for connecting external hard drives to a computer. eSATA requires different cables than standard SATA and slower maximum speeds. eSATA can transmit data at up to 1.5 gigabits per second, one-quarter of SATA's maximum speed and three times USB 2.0's maximum speed.