A hybrid car is one that uses more than one means of propulsion. At the moment, that means combining a normal petrol or diesel engine with an electric motor. The chief advantages of a hybrid are that it uses less fuel and emits less CO2 than most conventional non-hybrid vehicles.
It has Rechargeable batteries. Once the battery has been depleted, the vehicle can slip back to being a regular fuel-fed hybrid and recharge its batteries using the gasoline-powered motor as a generator. The big difference here is that you can also plug it in and recharge the electric motor instead of using the engine to charge it up.