Best explained by the Elder god "These gates twist space, laying a path
across great spans"
Teleportation gates are all over Nosgoth and once activated allow you
to instantly go from one to another.
Once activated (by standing on the circle symbol on either side of
it) you can then use it, however in order
to travel between gates both gates must be active.
Each gate has its own symbol, this is to identify its location in Nosgoth.
Each gate also has its own room, symbolised on the entrance door by
a sun like symbol.