Round heads are domed and look like half of a sphere. Slotted drive has a simple slot for a flat bladed screw driver.
A corrosion resistant steel alloy. The most common stainless steel for general hardware use.
A low carbon steel for general use. Zinc plated for moderate corrosion resistance.
Solid brass. An alloy of primarily copper and zinc with good corrosion resistance. Used mostly in decorative and electrical applications. Exact color varies.
Screws with machine threads for use with a nut or in a tapped hole.
Screws with an Allen wrench drive.