A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data.

An SSD emulates a hard disk drive interface, thus easily replacing it in most applications. An SSD using SRAM or DRAM (instead of flash memory) is often called a RAM-drive, not to be confused with a RAM disk. Recently, NAND based flash memory has become the standard for most SSD's.

The original usage of the term "solid-state" (from solid-state physics) refers to the use of semiconductor devices rather than electron tubes but, in the present context, has been adopted to distinguish solid-state electronics from electromechanical devices. With no moving parts, solid-state drives are less fragile than hard disks and are also silent (unless a cooling fan is used); as there are no mechanical delays, they usually enjoy low access time and latency.

Wiki:http://en.wikipedia.org/wiki/Solid-state_drive