The C128 is a computer system with a keyboard, external power-supply and a motherboard. The C128 computer has two processors, a 8510 and a Z80. The C128 has three different operating modes: C64 mode, C128 mode and CP/M mode.
The C128 is the successor of the Commodore C64. If you compare the C128 with the C64 the C128 has a bigger memory, faster processor and better graphical possibilities. But the strong success of the C64 prevented a breakthrough for the C128.