The visa is a color sticker pasted into your passport by the US consul abroad. It shows the classification status you will have when you're admitted to the US.
If your visa has expired and you're planning to travel outside the US, you'll need to renew your visa.
Your visa will contain:
a. Identifying information to match the information on your passport photo ID page (name, birthdate, passport number, etc.)
b. The type or class (J-1, H-1B, etc.) in which you plan to enter the US
c. The number of times you are permitted to request entry to the US (multiple or single)
d. An expiration date
e. The institution where you will work (Emory University) or the Exchange Visitor Program number for Emory
f. Notification of whether or not you will be subject to other immigration regulations (e.g., 2-year home residency requirement)