It is easier to keep an object moving which is already in motion than to move an object from rest ?  Explain?

When you move any object from rest to some velocity, you have to apply the force required to provide the acceleration required to attend that velocity in that time. Also you have to overcome the static friction. But when the body is in motion you have to apply force only to overcome the kinetic friction (which is less than static friction). That's why it is easier for to keep a moving object mobile while it is difficult to move an object which is in rest.