A plug-in hybrid electric vehicle, short PHEV, is a car which uses an electric motor lie a purely electric car plus some other motor, usually a combustion engine. It can recharge, like a pure electric car, from grid power. But also by the other engine or even convert some of the energy won by decelerating.
As noted in the article about electric cars you might will a worse turnover when living in an area where the electricity is created by the use of fossil fuels. But since plug-in hybrids also uses the combustion engine to recharge, you are still "greener" than with a car running on pure electric, if the efficiency of the electric car is worse than a car running on gas, and the electricity for recharging the electric car is mainly made from fossil fuels. Might help to not let the climate change become as worse as predicted without cutting carbon emissions.