The Surface Pro and RT tablet don’t have the wired ethernet connectivity. If you take the device to a place that has internet connection via Ethernet cord, with no wireless network. You need to use the Ethernet jack to access internet.
With USB to Ethernet Connector, you can add Fast Ethernet (RJ45) capable port to get full 10/100 Mbps Fast Ethernet performance for your Surface tablet.
* For Windows RT, ASIX had released Plugable USB2-E100 Driver for all Windows RT ARM devices, such as Plugable USB 2.0 to 10/100 Fast Ethernet LAN Wired Network Adapter, and that worked great,but Microsoft has asked that this driver no longer be distributed in the internet. So there is no Related accessories working for RT version since now.
* For Surface Pro Windows 8, the Cables To Go JETLan USB 2.0 Fast Ethernet Adapter and these USB ethernet adapters works perfect.