Green cars are eco friendly vehicles that cause lesser harm to the environment than the regular ones that run on gas/diesel and equipped with combustion engines. It is also a term for low carbon emission vehicles and other zero emission vehicles. These cars use alternate fuels and comprise of battery electric vehicles, hybrid electric vehicles etc. Green cars use energy that is not fossil fuel and emits less carbon. Battery powered cars and plug in hybrids have become very popular in the category of green cars.
You can even transform your regular car into a green vehicle by using less carbon intensive fossil fuel and mixing renewable fuel. Generally public transport is not considered in this category. Another example of a green automobile is a solar vehicle that runs on energy obtained through solar panels. But they are not meant for regular transport. Use of green cars is good for health and environment.