A quantity which has only magnitude and no direction is called scalar quantity. Example: mass

The vector which has a starting point or a point of application is called a polar vector. Velocity may be regarded as a polar vector.

The vectors which represent rotational effect and act along the axis of rotation in accordance with right hand screw rule are called axial vector. Axial vector will have its direction along its axis of rotation depending on its anticlockwise or clockwise rotational effect.

The magnitude of a unit vector is unity. It just gives the direction of a vector. A unit vector has no units or dimensions.

A zero or null vector is a vector that has zero magnitude and an arbitrary direction. The velocity vector of a stationary object is a zero vector.