Looking Glass servers are computers on the Internet running one of a variety of publicly available Looking Glass software implementations. A Looking Glass server (or LG server) is accessed remotely for the purpose of viewing routing information. Essentially, the server acts as a limited, read-only portal to routers of whatever organization is running the LG server.
Typically, publicly accessible Looking Glass servers are run by Internet service providers (ISPs) or Internet exchange points (IXPs).
References
Looking Glass server Wikipedia(Text) CC BY-SA