The 74HC595 is an octal (8) D type Flip Flop. Each D Flip Flop circuit has a non-inverting 3-state output (pins Q0-Q7). When the !OE pin is high, the outputs switch to their hi-impedence off state. Multiple 74HC574 chips can have their outputs connected in parallel as long as only one (the active chip) in the arrangement is active at any time. In this way, the 74HC574 can function in a parallel bus fashion. When the !OE pin is low, the contents of the D latches, are made available to the output pins..
