The Rebel Alliance is a paramilitary organization within the Pocket Universe who have two main enemies. One is the Kurgan Caliphate because that government forcibly converts people to it's fanatical, fundamentalist version of the Church of the True God. The other is the robotic Cylons because they want to exterminate Humans.
The Alliance maintains a fleet of Hyperdrive-equipped ships, mainly Bulk cruisers and a few Asteroid ships, that stay very close to the Warp Barrier at the edge of the local universe when not on the warpath. They also maintain squadrons of Starfighters and TIE fighters.
The Rebel Alliance also includes planet-based guerrilla forces on Cylon- and Kurgan-controlled worlds.