Intel's 'K' chips are unlocked, allowing enthusiasts who want to overclock to get even more performance out of their CPU.
'KF' SKUs are also unlocked, although they don't come with integrated graphics. That explains why KF CPUs are cheaper, but it's also important if you use your CPU for video editing.
Since KF SKUs have no integrated graphics, you'll need to rely on a discrete graphics card for (as an example) video encoding.