When the black hole has a companion star orbiting it, matter from the companion can form a disk of material close to the black hole. These disks often radiate brightly from the heat of friction. Clumps of material from the companion star, if they fall onto the disk, can result in the occasional ejection of powerful jets of charged particles, sometimes at speeds approaching that of light.
Swirling around the black hole like water circling the drain in a bathtub, the matter compresses and the resulting friction turns it into plasma heated to a billion degrees or more causing it to glow and radiate energy.