The conversion of reactants into products is the forward reaction. The conversion of the products into reactants is the reverse reaction. As the reaction proceeds, the rate at which reactants go to products becomes equal to the rate at which the products go to reactants. Chemical equilibrium is reached at that point. IF the arrows are of unequal length, the longer arrow will point to the side that is favored.
Catalysts speed up the forward and reverse reactions equally.
17.11 Equilibrium constants are used to tell whether reactants or products are favored in a reaction. The value of Keq depends on the T and changes when the T changes.