^Condition to start relative motion
Suppose a body A at rest over another body B. Let the limiting friction acing between them is fLAB. If a net force F acts on A which tends to start motion of A relative to B then the condition to start motion of A relative to B is F > fLAB. If F > fLAB then A will remain at rest relative to B. However if
F > fLAB then A accelerates relative to B & a kinetic friction between A & B acts.