Is friction reduced when you grease a bike chain?

Friction is the force that opposes the relative motion of two objects in contact. In the case of a bike chain, the two objects in contact are the chain and the teeth of the gears. When the chain is dry, there is more friction between the chain and the gears, which makes it more difficult to pedal. When the chain is greased, the grease reduces the friction between the chain and the gears, which makes it easier to pedal.

The reduction in friction also helps to prolong the life of the chain and the gears.