Speed Force

The Speed Force is an energy field that connects all speedsters, and grants all speedsters their power.

History
When the particle accelerator blew up, it connected Barry Allen with the Speed Force, giving him the powers to become the Flash. At that same moment, the particle accelerator hit Roscoe Hynes, but instead of giving him powers, it trapped Roscoe inside the Speed Force.

During his early years as the Flash, Barry became stuck in the Speed Force. Cisco Ramon had to use his powers to help get Barry out of there.

Within the Speed Force
Cisco Ramon had a vision of Roscoe Hynes, trapped in the Speed Force. Cisco used his powers to help Barry Allen enter the Speed Force and rescue Hynes, but Hynes ended up trying to kill Barry. Barry managed to defeat Hynes, and left him in the Speed Force.