The force that opposes motion between two surfaces in contact is known as friction. This resistive force arises due to the interactions between the surfaces at a microscopic level and can vary based on the materials involved and the nature of their contact. There are different types of friction, including static, kinetic, and rolling friction, each with unique properties. Friction is essential in daily life, enabling movement and providing traction, but it can also result in energy loss as heat in mechanical systems, affecting efficiency.