The Stick of the Bow is the base of the bow. Modern bows are made from Hardwood, such as pernambuco and brazilwood. Cheaper bow sticks are made from fiberglass.
The Screw is at the end part of the bow. You loosen/tighten the horsehair. The horsehair actually comes from Horse Hair, a horse's tail specifically. The color of horsehair is commonly white, some can be black as well. Some prefer a bit of a mix of black and white, known as "salt and pepper".
The Tip is the sharp looking bow found at the end of the stick. It's the most fragile part of the bow.
The Frog is the heaviest part of the bow. It is the part where the screw is located. While playing the violin, the bow is held at the Frog part when it is moving across the strings.