The main difference between these two things is that a passport is a proof of citizenship, while a green card is a proof of permanent resident status.

A U.S. passport is an identity card issued to U.S. citizens by the U.S. government, proving that the holder is a legal U.S. citizen. A U.S. passport is printed with the holder's basic information and the signature of the U.S. government. The holder can use it for travel, study, work, etc.

The U.S. Green Card is a U.S. permanent resident identity card, issued by the U.S. Immigration Service to applicants who meet the requirements of immigration laws, proving that they are legal permanent residents of the United States. Holding a U.S. green card means that the applicant has obtained permanent residence in the United States. They can live, work, and study in the United States, and enjoy some benefits, such as medical care, education, etc.