What is limiting friction

As you start increasing the force on an object from 0 N it the object will stay at rest and at a certain magnitude of force the object will start moving. The friction acting on that object is known as limiting frictional force. The magnitude of this frictional force is equal to the force that we apply on the object as it just start to move.

It's important to note that the limiting frictional force is the largest frictional force act on that object in the above explained process. The dynamic frictional force (the frictional force acting on an moving object.) is always less than the limiting frictional force.