Lubrication
Lubrication is adding a slippery layer between two surfaces so they slide instead of grinding.
Think of it this way
Butter spread on a hot pan sits between the pan and food as a slippery layer. The food slides around instead of sticking and tearing. That thin film of fat keeps the two surfaces from grinding together. Less friction means easier movement and less damage to both surfaces.
Explaining lubrication by grade level
Rub two metal pieces. They catch and drag. Now add oil between them. They slide with ease. The oil makes a thin, slick coat. That coat stops the parts from grinding.