A Many measurements can be described by using just one number.
Examples are temperature, the wavelength of light in a laser beam, and one's weight or height.
There are also other things that need both a direction described as well as the number that tells you how much of whatever you have. A simple example would be the movement of an airplane in flight. Vectors are shown as a line segment with an arrow head at one end. In this way, the direction of the vector is obvious. For example, imagine a plane flying horizontally in a northerly direction at 500 miles per hour.