Wood screws have large threads for use in wood.
Flat heads are countersunk (cone shaped under the head) with a flat top. Slotted drive has a simple slot for a flat bladed screw driver.
Round heads are domed and look like half of a sphere. Slotted drive has a simple slot for a flat bladed screw driver.
Bits for slotted screws.
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.