If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or pressure, then the equilibrium shifts to counteract the imposed change and a new equilibrium is established.
T increased (decreased) → endothermic reaction (exothermic) favoured! Concentration of a species increased (decreased) → the reaction which makes disappear (appear) this species is favoured! P increased (decreased) → reaction which decreases (increases) the volume is favoured!