Planetary chauvinism is a way of thinking which says that Earth and life on Earth is the most important and special thing in the universe. It's like when someone has a favorite family member and they think that person is the best, and ignores or doesn't think much of other family members. That's what planetary chauvinism is like. People who believe in planetary chauvinism ignore or don't think much of other planets, stars and galaxies because they think Earth is the most important and special.