Flat heads are countersunk (cone shaped under the head) with a flat top. Phillips drive is x-shaped for installation with a phillips screw driver.
The most common stainless steel for general hardware use.
A highly corrosion resistant grade of stainless steel. Ideal in salt water and chlorine environments. More expensive than 18-8.
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.