The real length of path traversed by a body in a sub interval of time is called as distance. It is the real path travelled by an object among its final and initial positions. It is a scalar function and its unit in SI is meter. Displacement can be positive, zero or negative but distance is always +ve. If a particle goes in a straight line without modification in its direction, the value of displacement is similar to the distance travelled. Or it is usually less than it. Therefore, Displacement   distance