A Work Permit is a document that allows a foreign national to work legally in the United States. Foreign nationals who are not U.S. citizens, but who are authorized to work in the country, need to obtain a valid work permit. The application for a Work Permit is made through a specific form that is sent to the United States Citizenship and Immigration Services (USCIS).

Foreign nationals who may apply for a Work Permit include those with a Permanent Residence (Green Card), those who have a temporary work visa, and those who have asylum or refugee status. The application process and requirements may vary depending on the applicant's immigration category and visa terms.

The Work Permit is valid for a determined period of time and must be renewed before its expiration date. It is also important to note that the Work Permit is not the same as a work visa and does not grant the foreigner the right to enter or remain in the country.

Requirements to obtain the Work Permit 

The requirements for obtaining a U.S. work permit may vary depending on the category of immigrant and the type of application being made. In general, some of the common requirements include:

1. Be eligible to work in the United States: This means that you must be a U.S. citizen, a lawful permanent resident, a foreign national with a temporary work permit, or a foreign national authorized to work in the United States.
2. Complete the appropriate application form: You must complete the appropriate work permit application form, such as Form I-765.
3. Provide necessary documentation: You must provide documentation that demonstrates your eligibility for the work permit, such as prior employment authorization, a valid job offer, or an immigrant petition approval.
4. Pay the corresponding fees: Applicable application and processing fees are required to be paid.

It is important to note that there are several categories of immigrants who are eligible to apply for a work permit in the United States, including asylum seekers, spouses and children of U.S. citizens, among others. Therefore, it is important to consult with an immigration attorney or government agency to learn the specific requirements for each category of immigrant.