Simply said product binning
is a way to select and categorize products mainly used in the CPU and GPU business.
Normally a company like Intel designs a chip to function at a max specific speed, for example this 3.5Ghz quad core CPU, not all the CPU's that come off a wafer
will meet the specs but can be sold as a slower version, for example a 3Ghz quad core. That process is called binning.
In this case it means that someone (an overclocker named 8Pack) filtered out the best performing chips of them all (or at least they claim) so they can be sold as such by Overclockers, this process is also often called cherry picking. These chips perform allot better then what they were originally designed for, it could be that this chip does over 5Ghz when you use LN2 to cool it where a lesser chip wouldn't be able to run at that speed under the same conditions.
Anyway, unless you are planning on (extremely) overclocking the CPU you are better off buying the standard chip for less if that is an option.
Edit: Clarified allot of stuff.