How does oil between machine parts reduce friction?

yeah what he said. I was going to say something like that but he explained it better.

Oil as you might notice is used in moving parts in machines.

The reason being is that oil is a smooth type of liquid.

So when machine parts are moving with oil on them, the oil allows the machine parts to move more smoothly. So when there is a squeaky noise on a moving part on a machine, mechanics/workers often put oil to make it more smooth because the moving parts are rubbing off on each other.