A Mother Box was a device used by Darkseid on his plan to invade Earth. Parademons were sent to earth to place them on several cities, such as Metropolis and Central City. When activated, Parademons were able to fly trough it from Apokolips.
The energy from one badly damaged Victor Stone, and caused the machine that was attempting to heal him to fuse together with Victor, turning him into Cyborg. Because of this, he gained technopathy and learned about Darksied and the Mother Boxes. Cyborg retains the ability to "boom" where he needs to thanks, to the data upload.