Each is a different faction in the Editors setting.
The Transpace Guard and the Time-Space Administration Bureau are the two big superpowers in a Meta Cold War, with the IDPKB between them.
SUE's are Mary-Sue's, that crop up in dimensions and need to be neutralized, one way or another.
The ATN are the Allied Timelines for Non-Determinism. Instead of simply finding other Dimensions to bring into their fold, they go back in time, assassinate key figures or drop off a bunch of advanced technology, and guide history so that the branching timeline becomes a world with the military resources, industrial infrastructure, and advanced science that will be useful in their war with the Closers.
The Closers for their part are just super-advanced Carthiginians.
And the Combine is from the Half-Life series of videogames.