It’s important to understand the concept of immigration status and the consequences of violating that status. Being aware of the requirements and possible consequences will make it more likely that you can avoid problems with maintaining your status. Every visa is issued for a particular purpose and for a specific class of visitor. Each visa classification has a set of requirements that the visa holder must follow and maintain. Those who follow the requirements maintain their status and ensure their ability to remain in the United States. Those who do not follow the requirements violate their status and are considered “out of status.” For more information see “Out of Status”. In Status means you are in compliance with the requirements of your visa type under immigration law. For example, you are a foreign student who entered the United States on a student visa. If you are a full time student and pursuing your course of study, and are not engaged in unauthorized employment, you are "in status." If you work full time in your uncle's convenience store and do not study, you are "out of status."
Source: U.S. Department of State.