SSD (solid state drives) utilize 'flash storage', they're one in the same. The flash memory commonly used in SSDs are of the NAND variety, which utilize floating-gate transistors (i.e. there is a floating node in between the gate and the rest of the transistor, in which then electron tunneling is used to write a 1 or 0 to the floating node; which to be utilized as memory, is then subsequently read from and can be overwritten).
//Electrical engineering student
EDIT - And just to be clear, the MBA currently does use an SSD, but its flash chips are organized a little differently and into a blade-like structure (longer than it is wide). This differentiates itself from common 2.5in SSDs, like the ones that are used in MBPs or iMacs