What is it? A standard or flathead screwdriver is a screwdriver with a horizontal end piece. It is used primarily on slotted screws which are screws with a single groove across the middle.
Who uses it and why? Flathead screws are used for precision work. They are commonly used by contractors since flatheads are often found on door hinges. (source) It can also be used for other tasks such as opening cans or scraping paint. (source) What materials can they be used on? Materials that flathead screwdrivers can be used on are brass, steel, and aluminum.
How is it used? It is used on slotted screws by placing and turning. What are their distinctive features? There are no distinctive features since this is the most common screwdriver. Where can I buy it? Home Depot How much does it cost? $3.99-$21.37 (source) Works with Slotted screws