How would the frictional force vary for an object being slid across the floor, for example?  Starting with an applied force of zero and then increasing it (1), we see that the static frictional force increases as well, always just enough to counteract the applied force.  Once the applied force, and therefor the static force, reaches the value m_SN (2), the object will start to slide, and the frictional force will become kinetic in nature (heavy dotted line)(3).  If the applied force were to continue to remain constant or even increase, the kinetic frictional force would remain at m_KN and the object would accelerate (4).  However, the tendency of a mover is usually to let up once the object starts to slide, and so we might expect to move to the left along the lightly dotted line (5).  Now, so long as the applied force value is greater or equal to the kinetic frictional force, the object will continue to slide, but if the applied force is allowed to become smaller than m_KN (6), the object will decelerate and eventually come to rest, at which point the frictional force immediately resumes its static nature, thus dropping to whatever value F_APPLIED has (7).