Explain - “Static friction force opposes impending motion”

Explanation

Consider motion of an acceleration
Let a box is lying at bottom of compartment of train.
if there was no friction bottom of train would have moved further box will try to retain its position due to inertia and would collide with rear part of compartment but this do not happen in dayh to day life .
Thus if can be said that static friction force opposes impending motion.
this impending motion is opposed by static friction force `(f_(g))` This friction force provide equal acceleration in opposite direction of acceleration of train keep box stationary