The leading letter and following number lays out the chipset.
Bxx boards are business series, fairly cheap and not very quality overall for performance systems. Also locked.
Hxx boards are higher quality, but still locked.
Both B and H series boards are limited to a single graphics card as well.
Zxx series boards allow for overclocking as well as SLI.
The numbers represent the series each board is a part of. H97, or Z97, are the boards I recommend for non OC and OC respectively.
Since you are looking at a 4460 (I recommend a 4590, or a 4690K over it) look at the ASRock H97 Pro4. For unlocked processors, something like the Z97-A.