An Employment Authorization Document (EAD), commonly called a work permit, is a legal document issued by the United States Citizenship and Immigration Services (USCIS) that grants foreign nationals the right to work in the US for a specific period.
Whereas EADs are documents that prove you are authorized to work in the US, regardless of your immigration status, work visas are types of nonimmigrant visas, such as H-1B, L-1, or O-1, that allow you to enter the US for a specific purpose and period.
Also, because green card holders awaiting an adjustment of status are not considered unauthorized immigrants, they are not required to obtain an EAD to work in the U.S. while awaiting their adjustment of immigration status.
While DACA recipients (i.e., individuals who have received Deferred Action for Childhood Arrivals) are perhaps the most well-known class of persons eligible to work in the U.S. under an EAD, other persons eligible to work with them include, but are not limited to, certain refugees, asylees, spouses, fiancés, and dependents of certain non-immigrant visa holders.
Various application requirements and timelines may differ based on the type of application (e.g., refugee, DACA recipient, etc.). Generally speaking, per the USCIS, the earliest you can file for an EAD renewal is 180 days before the expiration date on your current EAD, and they recommend that you submit your renewal application 120 before its expiration date.
Initial and renewal applications should be submitted on Form I-765 (Application for Employment Authorization), with a fee of $410. Subject to certain exceptions, you will likely also be required to submit an additional $85 biometrics fee.
Other than being authorized to work in the US, EAD holders are entitled to a number of rights, and employers are required to comply with a number of obligations towards their employees who work under an EAD.
Confidentiality: Employers are responsible for keeping all personal and immigration-related information confidential.