A glorb is a small, glowing orb, that is first mentioned by Dendy in I Am Dendy. Every robot needs a glorb inside them, it works as a form of battery, it has been stated that they are hard to come by.
In Let's Have a Stakeout, it is revealed that through the sewers of Lakewood Plaza, there is a room, guarded by a strong door, where many glorbs reside. Shadowy Figure is interested in harvesting them and their "incredible power", as an important part of some unknown plan. Mr. Gar reinforces the door to the room, making sure the glorbs are protected.
Lord Boxman has a room for processing glorbs, as seen in Villains' Night Out. He owns a lot of them, and says he tries to use them as efficiently as possible, for their rarity. It's part of a top secret project of his. It also seems that Boxman has a glorb inside of him, as shown on one of the monitors in the lab.
Glorbs can also be used to power machines, as shown by Fink's collar given to her by her boss, Professor Venomous, in the episode Villains' Night In. The collar, powered by a glorb, changes her appearance, gives her extra power and abilities, such as the ability to float, and surrounds her in a purple glow. However, this only works for a short time, and she is soon returned to normal.