Well, Le 3eme oeil, HSF is basically an acronym for heatsink and fan. A lot of older PCs had CPUs that ran so cool, that they only needed a heatsink for some thermal dissipation. The heatsink is the metal block between the fan and CPU, or just a metal block on the CPU if you have one of these older PCs.
Todays CPUs require a much more effective cooling system, so they mount fans on to the heatsink to provide better cooling. It works quite well. So, in todays terms, CPU fan and heatsink usually go together as the same thing.