Employment Authorization Document
An Employment Authorization Document (EAD), EAD card, known popularly as Work Permit, is a document issued by United States Citizenship and Immigration Services (USCIS) that provides its holder a legal right to work in the United States of America (a holder can work as long as they carry an unexpired valid EAD and maintain their Legal Status in the US). An EAD shouldn't be confused with a green card (which indicates that its holder is a Legal Permanent Resident of the US).
An Employment Authorization Document is issued for a specific period of time based on an alien's immigration situation. Generally it is valid for one year and has to be renewed. If an alien possess a valid EAD, he or she is authorized to freely work in the United States without having their employer to file a non-immigrant worker petition. Currently EADs are issued in the form of a standard credit card-size plastic card enhanced with multiple security features. EAD cards contain some basic information about the alien: name, birth date, sex, immigrant category, country of birth and photo, alien registration number (A number), card number, restrictive terms and conditions and dates of validity.
Although foreign nationals with an EAD can lawfully work in the United States for any employer, it is also possible for an alien to work for a specific US employer without EAD (examples are H-1B, L-1, or O-1 US visas).