NPTF tapered pipe thread is commonly found in many industrial and agricultural markets across North America.
Tapered threads seal by an increasing interference of the threads as the fitting is tightened and the tapers engage.
Pipe sealant is often used to ensure a good seal along the crests of the threads and to prevent galling (binding).
NPSM threads have the same dimensions as NPTF threads but lack the taper, and so rely on a cone shaped seat on the female fitting to seal against a chamfered male.
NPSM threads are typically used on female swivel adapters and are most common on farm equipment.