So you filed all your paperwork, and finally you received an approval notice. You may be thinking, “Yipee, I have a visa!” Well… not so fast.
The approval of your application/petition for a visa means that you are now in valid status, however, having a visa and being in immigration status are two different things. Nonimmigrant status is a form of immigration status that may be granted when you are already in the Unites States or you are arriving in the United States. It is usually indicated on an approval notice from U.S. Citizenship and Immigration Services (USCIS) and a Form I-94, and will include an expiration date. It allows you to legally remain in the United States as a nonimmigrant.
A visa, however, is a document placed in your passport by a U.S. consular official. It permits you to enter the United States and if your visa is a multiple-entry visa, you can use it to travel into and out of the United States repeatedly. In order to obtain a visa, you have to apply for it.
So a visa is basically a travel document that allows travel and re-entry into U.S. It can ONLY be obtained outside the U.S. If you decide to travel, you will have to make sure that you can get a visa in order to re-enter the U.S. Ideally, you would need to obtain your visa in your home country.