A hybrid system refers usually to the combination of two or more energy generating applications (e.g., diesel generator and/or wind turbine with PV system) to provide electricity at all times, or in all critical times.
Generally, a hybrid system will be designed to ensure reliability (e.g., hospitals, industrial processes, computer operations), where one energy source (e.g., PV from the sun, wind) is intermittent, ie, not always available.