Distance is the actual path travelled by a body in a given time. Consider a body travelling from A to B along any path between A and B. The actual length of the path that a body travels between A and B is known as the distance. Here if the body goes from A to B via C, the distance travel will be ACB. The distance travelled will be different for different paths between A and B.

The distance travelled by a body in unit time is called its speed. 
Therefore, speed = Distance/Time

(a)    Uniform Motion : A body has a uniform motion if it travels equal distances in equal intervals of time, no matter how small these time intervals may be. For example, a truck running at a constant speed of say, 20 m/s, will cover equal distances of 20 metre, in every second, so its motion will be uniform.
If it moves along a straigth line with a constant speed it is said to be in uniform motion.

(b)     Non-Uniform Motion : A body has a non-uniform motion if it travels unequal distances in equal intervals of time. For example, If a car moving on a highway , we will find that it covers unequal distances in equal intervals of time. It covers :
5.9 metre in the 1st second,
15.7 metre in the 2nd second,
30 metre in the 3rd second, and so on.
If the speed of an object is not moving along a straigth line  keeps changing, its motion is said to be non-uniform.

Uniform and Non-uniform motion can be shown graphically also

 Ex. 3 A body satrts from A and moves according to given figure. Time for each interval is : 

tAB = 2s, tBC= 3s, tCB=2s, tBA = 3s, tAD= 4s

The distance, speed are as follows for different path.

Ex.4    A car travels a distance of 100 Km in 25 minutes to reach a place then calculate the speed of the car : 
(A) 4 km/min         (B) 4 m/min          (C) 400 m/min         (D) None of these

Ex.5     If an object  travels with the speed 18 km/hr for 20 minute find the distance covered by the object.
Sol.    Speed = 18 km/hr, time = 20 min
    Distance = speed × time