Authorized Stay: A person's authorized stay is the time during which he or she is permitted to remain in the United States. The I-94 card shows the duration of the authorized stay indirectly; the INS officer inspecting the foreign national entering the United States will write the last day of the authorized stay after the word "until" on the card.

Date of Hire: The date of hire is the date a person actually begins providing services or labor in exchange for wages or other remuneration. Thus, a person is "hired" (for purposes of completing a Form I-9) on the first day of work, not the day of acceptance of a job offer.

Documents Evidencing Employment Authorization: The INS issues a number of different documents to evidence employment authorization. These documents are INS Forms I-688, I-688A, I-688B, and I-766.

I-94 Cards: An I-94 Arrival-Departure Card is probably the most important document a foreign national holds while he or she is in the United States. It is more important that the visa, because the visa only shows the status for which the foreign national was eligible to apply at the border. A person may have many visa, depending on how many times he or she has entered the United States. The I-94 card shows the immigrant or nonimmigrant status actually granted to foreign national. The status held by a person determines the activities in which the foreign national may engage while in the United States and the duration of the authorized stay in the United States .

Overdocumentation: Employers are prohibited from requesting "more or different" documents from employees for I-9 purposes. This means employers cannot (a) refuse documents simply because they want to see different documents (unless they have reason to believe that the documentation is fraudulent or does not apply to the employee in question), (b) ask to see specific documents, or (c) ask to see additional documents, such as by reviewing more than the minimum documents permitted for I-9 purposes: one List A document, or a combination of one List B document and one List C document. Employers who overdocument employees may be fined by the Office of Special Counsel. Fines range between $100 and $1000 for overdocumentation occurring before March 15, 1999, and between $110 and $1,100 for overdocumentation occurring on or after March 15, 1999.

Overstay: A person overstays when he or she remains in the United States past the expiration of his or her authorized stay.  A person who has overstayed is also unlawfully present in the United States .

A person who overstays by as little as one day must, from that time on, obtain all visas from the U.S. Consulate at his or her home country. The person will no longer be able to apply for a visa in neighboring countries such as Canada or Mexico. For most people, this consequence is not serious. However, for nationals of countries far distant from the United States, such as India, China or Russia, where the U.S. Consulates are badly overworked and backlogged, and where visa applications are subject to higher scrutiny than at other Consulates, this penalty may be quite serious.

Since 1996, a person who overstays more than six months is banned from returning to the U.S. for a period of three years once they leave the country.  A person who overstays more than one year is banned for 10 years from returning to the U.S.  These are horribly restrictive penalties imposed upon overstays and actually encourages people not to leave the U.S. but to remain in an illegal status for fear of not being able to return to their homes and families. There is a waiver available if extreme hardship can be shown to a U.S. citizen or lawful resident.

Port-of-Entry: This is a place where a foreign national may gain entry to the United States, such as an international airport, or border-crossing between Canada or Mexico and the United States .

Status: Foreign nationals can hold:

(1) immigrant status, which means they intend to reside in the United States permanently. This is also called permanent resident status. It is evidenced by Alien Registration Cards, also called "greencards", so immigrants are sometimes also called greencard holders.

(2) nonimmigrant status, which means that they may reside in the United States only temporarily. Most nonimmigrant statuses are valid for less than seven years.

Unlawful Presence: A person is unlawfully present in the United States is he or she illegally entered the United States; or overstayed in the United States after the expiration of his or her authorized stay.

If a person is unlawfully present in the United States for more than 180 consecutive days, he or she is barred from re-entering the United States (once he or she leaves) for three years. If a person is unlawfully present in the United States for over 365 consecutive days, he or she is barred from re-entering the United States (once he or she leaves) for ten years. Note that these penalties do not attach until the person leaves the United States; thus, if the person never leaves, the penalties take effect.

Visa: A visa is a document issued by a U.S. consulate abroad to foreign nationals. It is comparable to a ticket, because it shows the status that the bearer wants to have when admitted to the United States but does not guarantee admission. CIS officers stationed at ports-of-entries around the world have the right to question all travelers entering the United States to determine whether the foreign national is entitled to be admitted, and may chose to refuse entry to any foreign national.