Measurements in physics are said to be either scalar or vector quantities. Scalar quantites only have magnitude, examples include temperature, mass, volume and speed.
Vector quantities have both magnitude and direction.
Examples of vector quantities are force, diplacement, acceleration and velocity. When giving a value to a vector quantity, the direction musst be given in some way as well as the magnitude. Usually velocity is represented graphically by an arrowed line. The length of the line indicates the magnitude and the direction of the arrow the direction of the velocity. Sometimes velocity can be given as a negative quantity and this would imply that it is moving backwards.