Employment authorization document
A Form I-766 employment authorization document or EAD card, known popularly as a work permit, is a document issued by the United States Citizenship and Immigration Services (USCIS) that provides temporary employment authorization to noncitizens in the United States.
A Form I-766, Employment Authorization Document, issued to an applicant for adjustment of status by USCIS in November 2018, and noting at the bottom that the card also serves as a Form I-512 providing for Advance Parole (EAD-AP combo card).
Image: EAD Not Valid Both Sides
A work permit or work visa is the permission to take a job within a foreign country. The foreign country where someone seeks to obtain a work permit for is also known as the "country of work", as opposed to the "country of origin" where someone holds citizenship or nationality.
Applying for working papers, 1908 (United States Children's Bureau)