A ZIF (Zero Insertion Force Socket) allows you to insert and remove chips easily from an existing circuits. These are often used for chip programmers or when you need to test a chip without damaging it. Move the lever up and chips drop right in. Move the lever down to 'latch' the chip in place.
This socket is designed for DIP chips of up to 40 pins and up to 0.6" wide. So really, its good for any size chip you'll find. What's nice about it is it can snap into an existing circuit board or socket that is designed for a 40-pin 0.6" chip so you may not have to redesign the board! This socket is gold plated so it will last a long time.