What is meant by soft strap and pin strap (HW strap) in a processor datasheet?
A pin strap in an Intel PCH type component is a configurable option selection that is selected by asserting a high or low logic level to some pin on the PCH at an initial time. For PCHs most pin straps are sampled by the PCH at time the RSMRST# signal rises from low to high. Pin straps are most often applied to pins that normally have other functionality during normal PCH operation. Sometimes pin straps are referred to as "hard straps". 

On the other hand in the PCH realm soft straps are configurable  option selections that are loaded into the PCH to select many different optional modes of both the hardware and the firmware components inside the PCH. The softstraps for a PCH are sourced from a dedicated section of the attached SPI Flash component. There is usually a tool that the product designer / manufacturer / OEM uses to configure the SPI Flash image including this dedicated section. The tool would be supplied by the PCH manufacturer.