Friction is Desirable: A friction is very much desirable to stop the body from its moving condition. If there is no friction between the contact surfaces then a body cant be stopped without the application of external force.

How is friction sometimes desirable?

In some cases, friction is desirable while in other cases, friction reduces the effectiveness of machines. Without friction, you would not be able to walk, the wheels on a vehicle would have no grip on a road surfacing and the vehicle would not be able to move forward.

What is friction desirable?

Friction is desirable in braking of a vehicle. As brakes are applied, friction between brake shoes and tyres opposes rotation of tyres and hence, forces it to stop.