Des=some/of the+plural (de+les->des) and de=of/from. J'ai des fraises=I have (some) strawberries but mes albums de photos=my albums containing photographs=my albums of photographs. "My album of the photographs" doesn't make any sense here. Another example : les maisons des villes = the houses of the cities but les maisons de Pierre = the houses of Peter Peter's houses. Hope it helps !