Static vs Kinetic Friction 

Friction is a force created by a surface which acts parallel to the surface and opposes all motion on the surface. There are two types of friction: static and kinetic/dynamic.
Static friction is the force of friction that prevents an object from moving on a surface when other forces are applied. It always perfectly balances any unbalanced forces parallel to the surface as long as those forces are below a certain maximum. The maximum force of static friction a surface can apply is given by the equation Fs ≤ μs*R where μs is the coefficient of static friction and R is the normal force on the object. If you push with a force greater than the maximum static friction, the object begins to move.
Kinetic or dynamic friction is the frictional force that acts on a moving object. This force does not change for a specific object regardless of the object's speed or other parallel forces acting on it. The equation for kinetic friction is Fk = μkR where μk is the coefficient of kinetic friction and R is the normal force. Kinetic friction can be thought of as the force required to keep an object moving, because applying a smaller force than the kinetic friction causes the object to have a net force pointing against its motion which slows it to a stop.