PureRun Cat6 cable is made with Pure Copper for the cleanest connection and most reliable quality. If you want your system to perform, get Pure Run cable. This SolidRun cable is rated to the highest specs for Cat6 passing fluke tests at 550MHz. Pure Copper better combats interference, packet loss, and other things that might slow down a network.
Cat5e vs. Cat6
Although Cat5e also supports a gigabit network, Cat6 features more stringent specifications to fight crosstalk and EMI. Crosstalk is the interference that happens inside the cable between the four twisted pairs of conductors that are wrapped around each other. EMI or "electromagnetic interference" is the interference from the environment. This can come from power lines, office flourescent lights, microwaves, etc. Cat6 also features a thicker gauge that protects you from such problems.
Plenum (aka CMP)
US law mandates that only certain kinds of cables may be used in 'plenum' spaces in buildings. These spaces are typically where a lot of the building's breathing air passes through (typically in between floors and above ceilings). CMP or plenum wiring may only be used in these spaces because they are rated for low smoke and fire retardation. This cable is UL rated to be used up to code in these plenum spaces.