The Gamma Quadrant is located between the 9 and 12 o'clock positions if the plane of the galaxy were seen as a clock face with the 6 o'clock position bisecting the Sol system.
Its closest point to Earth is located approximately 30,000 light-years away. However, the stable Bajoran wormhole links the Idran system in the Gamma Quadrant with the Bajoran system in the Alpha Quadrant.
The quadrant was first explored by the Starfleet's Quadros 1 probe in the 22nd Century. A large portion of the Gamma Quadrant is under the control of the Dominion, but it is believed that some minor powers exist on the fringes of their space.