The VT Username Identifier (pid@vt.edu) and network password are used to access the eduroam WiFi network at Virginia Tech and at thousands of other locations around the world. 

Your VT Username (PID) and network password are also used to authenticate to the Virtual Private Network (VPN) which provides access to university resources that would otherwise only be available if you were physically located on campus. For the VPN, you'll want to connect "VT Traffic over SSL VPN" in most cases.