A portal is a kind of doorway from one location to another. In many cases they are often Plot-Holes, which are tears in the fabric of the Narrative. Other times they are stated as portals, which are tears in space-time. Some Characters are able to create portals, while some factions, such as The Imperium, rely heavily on portal technology for travel.
Portals can come in a variety of visual styles. The Imperium use Dream Gates that create shimmering flat portals[Tales 1].
Portals lead from one location to another. Imperium portals can stretch any amount of distance[Tales 1].