The term loopback (sometimes spelled loop-back) is generally used to describe methods or procedures of routing electronic signals, digital data streams, or other flows of items, from their originating facility quickly back to the same source entity without intentional processing or modification. This is primarily intended as a means of testing the transmission or transportation infrastructure.

Examples of applications include the following:

A method of performing transmission tests of access lines from the serving switching center, which method usually does not require the assistance of personnel at the served terminal.
A method of testing between stations (not necessarily adjacent) wherein two lines are used, with the testing being done at one station and the two lines interconnected at the distant station. Commonly called loop around when the interconnecting circuit is accessed by dialing.
A patch cable, applied manually or automatically, remotely or locally, that facilitates a loop-back test.
A communication channel with only one endpoint. Any message transmitted through such a channel is immediately received by the same channel.
eg someone as set a selftest runing on one of the servers or you have been hacked (but this is unlikley)
hope this helps. frank