Friction is primarily influenced by the normal force, which is dependent on gravity, meaning maximum friction force does relate to gravitational force. While friction is proportional to pressure and the coefficient of friction, it is independent of factors like velocity and surface area. The discussion highlights that friction can be complex, often requiring simplifications for analysis. An example provided is the unique situation of astronauts on a treadmill in space, where gravity is simulated using springs. Overall, understanding the relationship between friction and gravity is essential in physics.