We don't seem know much about the Beta Quadrant compared to the other Quadrants. In TOS it was suggested that the Klingon and Romulan Empires were in the Beta Quadrant, but by DS9 they both seem to be in the Alpha Quadrant. Plus if both those empires were in the Beta Quadrant, how would they be so close to the Federation to the Alpha Quadrant, to the point that Federation Starships can easily travel to both the Klingon and Romulan home worlds.

So what exactly is in the Beta Quadrant?