BSP stands for British Standard Pipe Thread, also referred to as Whitworth thread and is common in the commonwealth countries and Australia.  The NPT is most common in the U.S. and Canada. The BSP comes in two types:

•       BSPP for parallel, or straight threads
•       BSPT for tapered threads

BSPT port options are similar to NPT although are not interchangeable.  The main difference between BSP and the NPT is the angle of the pitch which is 55° in the BSP rather than 60° in the NPT.

Source: Wikipedia