Cyber Core, formally known as Comp Space, and generally abbreviated as CC, is a term introduced in Mega Man Star Force 3. A Cyber Core is described as the central-most part of an electronic device. Normally, EM Beings can enter Cyber Cores, however some cores are access-restricted because of maintenance or other reasons.
Most Cyber Cores are connected to the Wave World via the Wave Road. This, in turn, allows for easy access to the cores by EM Beings.