Friction acts friend:

1) If friction would not have been there, we would not have been able to walk.

2) Friction between the tip of the pen/pencil and a paper allows us to write.

3) It is necessary when you want to hold items and prevent slipping or sliding.

Friction as foe:

1) Tyres of cars and soles of shoes wear and tear out because of friction.

2) Friction between the different parts of machines produces heat. This can damage the machines.

3) Friction causes wearing of over-bridges at railway stations.