A person may work in the U.S. if he or she has either a non-immigrant working visa or an employment authorization document.

A person who has a non-immigrant visa that does not allow you to work in the United States, may be eligible to obtain permission to work if he or she has a particular skill that a prospective employer desires.  There are various avenues which may be utilized for the person or his or her prospective employer to obtain permission to work.

A foreign student with a F or M visa may obtain his or her school's foreign student advisor to obtain permission to work.

EAD Card
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 U.S.  It is not a green card.  EAD has limited employment and immigration-related privileges compared to a green card.

Employment Authorization Document is issued for a specific period of time based on alien's immigration situation.  In general, it is valid for one year and may be renewed.  If an alien possesses an EAD, he or she is authorized to work in the United States and the employer is not required to file a non-immigrant worker petition.

Foreign nationals with an EAD card may work in the United States for any employer.  It is also possible for an alien to work for a specific US employer without an EAD card.  For example, H-1B, L-1, or O-1 US visas may be available.

Who May Apply
If a person is not a U.S. citizen or a lawful permanent resident, he or she may apply for an EAD to establish the right to work in the United States.  Specific categories requiring an EAD include students seeking employment; applicants to adjust to permanent residence status;  people in or applying for temporary protected status;  fiancés and spouses of American citizens; dependents of foreign government officials;  J-2 spouse or minor child of an Exchange Visitor; spouse of an E-1/E-2 Treaty Trader or Investor and spouse of an L-1 Intra-company Transferee and asylees and asylum seekers; refugees.   USCIS issues EAD’s in specific categories:• EAD: This document establishes the right to work in the U.S.
• Renewal EAD: The person cannot file more than 120 days before the original employment authorization expires.
• Replacement EAD: This document replaces a lost, stolen, or mutilated EAD. A replacement EAD may also replace an EAD issued with incorrect information, such as a misspelled name.

Documentation
• Application Form I-765.
• A copy of Form I-94 Departure Record, if appropriate.
•A copy of the last EAD. If no prior EAD has been issued, the person may submit a copy of a federal government issued identity document, including as a passport with your picture, name, and date of birth; a birth certificate with photo ID; a visa issued by a foreign consulate; or a National ID document with photo and/or fingerprint. The identity document must show the face of the applicant and biographical information.
• Two identical color photographs taken within 30 days of the filing of the application.

How to Apply
The person must file Form I-765 (Application for Employment Authorization) by mail with the USCIS Regional Service Center that serves the area where you live. The applicant may also be eligible to file Form I-765 electronically.

Interim EAD
An Interim EAD is an EAD issued to an eligible applicant when USCIS has failed to adjudicate an application within 90 days of receipt of a properly filed EAD application or within 30 days of a properly filed initial EAD application based on an asylum application filed on or after January 4, 1995. The interim EAD will be granted for a period not to exceed 240 days and is subject to the conditions stated in it.

An interim EAD is not issued by local service centers. One can however take an infopass appointment and place a service request at local centers, asking for it if the application exceeds 90 days without an adjudication.