PHEV stands for Plug-in Hybrid Electric Vehicle. It is a type of vehicle that combines a conventional internal combustion engine (usually gasoline) with an electric motor and a large rechargeable battery. PHEVs can be plugged in to charge the battery, which allows them to run on electric power for a certain distance before switching to the gasoline engine for longer trips. This dual power source setup helps improve fuel efficiency and reduce emissions compared to traditional gasoline vehicles. PHEVs are seen as a transition technology towards fully electric vehicles as they offer the benefits of electric driving with the flexibility of an internal combustion engine for longer journeys. BYD PHEVs include Qin Plus and Song Plus. 

PHEV is not to be confused with HEV. HEV stands for Hybrid Electric Vehicle, which is a vehicle that combines a traditional internal combustion engine with an electric propulsion system. This combination allows the vehicle to be more fuel-efficient and produce lower emissions compared to traditional gasoline-powered vehicles. HEVs can switch between the electric motor and gasoline engine automatically to optimize fuel efficiency. BYD doesn't offer any HEV products in its portfolio.