ZIF stands for Zero Insertion Force. Check out the wiki entry here. ZIF sockets are commonly used to program microcontrollers or to test ICs. Most are familiar with ZIF sockets for DIP ICs. I’ve always found those to be rather redundant, breadboards worked just fine for me.
Since I started using more surface mount ICs, I tend to buy extras and also a bunch of breakout boards to go with it. That’s because I like to test out whatever new ICs I just bought. There’s no way to do that unless I solder the ICs onto at least a breakout board with header pins so that it’s breadboard friendly.
Well, not anymore. I’ve just bought myself 2 ZIF sockets for small outline ICs (SOIC) from eBay. Some manufacturers call it small outline package (SOP or even just SO) although, that shoud technically be referring to a smaller family of ICs (like SSOP or TSOP). Should have gotten these a long time ago. Would’ve saved me a lot of money and trouble.