This number provides information on the specifics of the processor. The fourth-generation Haswell starts with the number four, the fifth generation Broadwell with five, and so on. Those models labelled "HQ" (High Performance Graphics) offer high graphics performance, whereas models designated "U" (Ultra-low power) can be found in ultrabooks with low power consumption. Some models support virtualisation or Turbo Boost functions, which increases the processor frequency when needed.
