Wood screws have large threads for use in wood.
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.
Solid brass. An alloy of primarily copper and zinc with good corrosion resistance. Used mostly in decorative and electrical applications. Exact color varies.
Round heads are domed and look like half of a sphere. Phillips drive is x-shaped for installation with a Phillips screw driver.
Screws with large threads for use in sheet metal sometimes also used in plastic, fiberglass, or wood.
Screws for wood to wood fastening applications such as decks, docks, and ledgers, etc.