Tango said:Its a sheet metal self tapping screw. The blade on the end cuts through the sheet and the course thread grips onto the metal. If you are using stainless you might need some anti seizing paste if you ever want to undo them again. However that depends entirely what your screwing it into.
If its purely stainless your after because it does not corrode like steel, consider zinc coated screws they tend to be stronger and wear less.