one person driving a huge SUV or littering doesn't make a huge difference. However, when everybody gets the mindset that if they only pollute a little it is okay, then all that pollution adds up to a big problem.
hybrid cars run off batteries and gasoline (regular cars just have gas) so that they use less gas. They also have lower emissions because a lot of their power comes from batteries rather than fossil fuels (gas) which pollute and release carbon dioxide into the atmosphere