A permanent residency allows eligible immigrants to live and work in the United States. Permanent residents are commonly known as Green Card holders and there are certain rules they should respect to maintain that status. For example, they can travel overseas, but not for unlimited amounts of time, as it would risk their residency. A US citizen is allowed to vote, apply for federal employment and run for publicly elected positions. Some advantages that citizens have over permanent residents are a U.S passport and the right to apply for certain federal aid programs.