SLOW FLYER PROP or ELECTRIC PLANE PROPELLER
SLOW FLYER=low rpm, low forward speed, high static thrust (LOW kv motor)
EPP, possibly a faster plane, made for higher kv motors
adding to what Vernon has said, the SFP usually have a lower high-end RPM limit.
They typically provide more thrust at a lower RPM, but this comes with the lower RPM ceiling.
To think of these propellers properly, you must realize that there is an optimal RPM window for thrust...
Below that window, and the propeller is not generating significant thrust, and is very inefficient. Above that window, and it is taking a lot of force to turn, and it risks breaking.