If you’ve been told you have to leave the United States due to your status as an immigrant, you go through the deportation process. Deportation is just another word for removal. It’s a formal process, and the end result is that you must return to your country of origin. If you violate U.S. immigration laws, this is likely.
Although this process seems frightening, you are not without rights. In fact, you have the right to appeal the decision to deport you, and you have the right to apply for readmission after you go through a deportation.