An F-1 student is a nonimmigrant who is pursuing a "full course of study" to achieve a specific educational or professional objective, at an academic institution in the United States which has been designated by the Department of Homeland Security (DHS) to offer courses of study to such students, and has been enrolled in SEVIS (the Student Exchange Visitor Information System). Once the educational or professional objectives have been attained, the F-1 student is expected by the U.S. government to return to his or her residence abroad.
A student acquires F-1 status using a SEVIS I-20 form, issued by a DHS-approved school through SEVIS. Status is acquired in one of two ways: 1) if the student is abroad, by entering the United States with the I-20 form and an F-1 visa obtained at the U.S. consulate (although citizens of some countries are exempt from the visa requirement); or 2) if the student is already in the United States, by sending the I-20 form to the U.S. Ctizenship and Immigration Services (USCIS) with an application for a change of nonimmigrant status.
An F-1 student that complies with the immigration regulations is eligible for benefits such as: On-Campus employment, Curricular Practical Training (CPT), and Optional Practical Training (OPT). Further information is available on this website.

Remember, it is always best to check with an advisor in the International Programs Center whenever you are uncertain about immigration matters.