Difference Between Visa and Status
A visa is required for a foreign national to enter the United States. Without a visa, entry to the U.S. is not possible (excluding ESTA visa waivers).
For example, students need an F-1 student visa, intracompany transferees need an L-1 visa, and professionals need an H1B visa to enter the U.S.
After entering the U.S., some people need to change immigration status within the U.S. For example, F-1 students may graduate and change their status to H1B as a professional. (The status changes from F-1 to H1B.) Even though their status has changed to H1B, they do not have an H1B visa because they did not receive one. They have H1B Status only.
Therefore, if they leave the U.S., they must obtain an H1B visa from the U.S. Embassy or Consulate in their home country before they can return to the U.S. and work under H1B status.
In other words, while staying in the U.S., having status without a visa makes no difference. However, if you leave the U.S. (except for Mexico and Canada), you will need to obtain the appropriate visa to re-enter and maintain your status.