Advantages of friction:
Friction is very important part of our life, like if you want to hold anything , there should be friction  between your hand and the material. Even if we have to travel using a vehicle, friction is present between tyres and road.
To tie a knot, to type a letter, to write a word, there should be friction between your hand and the other body.
Though friction hinders the motion of the body, it must be present in our day to day life.
Disadvantages of friction:
In big machineries, friction should be strictly avoided for smooth functioning of the machine without any wear and tear.
In a running machine, between two metal parts or screws if they collide with each other, due to friction, chances are high that they rub against each other and there are chances of fire sparks.
How to avoid friction in machineries, what do they do?
Using lubricants:
Lubricants are fluids which reduces the frictional force between two objects. These are castor oil, ghee, grease, etc.
Lubricants when applied over metal parts will fill up the gaps in irregular surfaces between objects in contact and provides a smooth layer between two objects and thus reduces friction.
Lubricants are by design attached to the frictional portions in machinery as shown in the picture below:
Boy holding a goat image : Image by Sasin Tipchai from Pixabay -
Lubricant fitted machine :  Image by olafpictures from Pixabay  -
Spark image : Image by Free-Photos from Pixabay