Why does changing the concentration of a reactant or product cause an equilibrium shift in the direction.....?

the change in concentration  can be increased and decreased. whatever we do nature tries to correct and come to its regular condition. that is the principle in simple english. So when a reaction is at equilibrium and u increase the the concentration on the reactant side , it will take what u added and try throwing it to the prodect side , so the product increases as well and balances with the increased reactant so , that the reaction can go back at equilibrium.

When u increase or decrease the concentration , the equilibrium gets disturbed and is no longer at equilibrium. So the principle says that nature will try to undo what u did , but can only get close and not completly return to its preveous state of equlibrium but will reach a new state of equilibrium with different concentration of each of the chemicals.

do u have a test tommorow because i have one too, on the same thing lol , funny if we do go to the same school.