Falling out of status means you've violated the terms of your F-1 visa like dropping below a full course load, working illegally, or staying after your program ends without proper authorization.

 If you accrue more than 180 days of unlawful presence and leave the U.S., you could be barred from returning for 3 years; more than a year = 10-year bar.

 In some cases, you may be able to file for reinstatement using Form I-539, but you must act quickly and have a good reason (like illness or school error).

Once you're out of status, you are no longer legally in the U.S., and you begin accruing unlawful presence, which can lead to deportation or future visa bans.