can any one tell me the procedure of using the item catalogue option as a item description while def

dear friend as we know that whenever we have to define a new item first of all we check from which cataogry it belong to and then we define it and we also have to given the desription of an item that we are defining .... now i have heared from my senior that we can also use item catalogue option for description tell me is there any such kind of provision availiable and if so tell me how ???