Commodore 128
The Commodore 128 was featured as a 3 in 1 computer. The CPU could run at 2MHz, and address 128KB of RAM. This was largely taken from the 'B' line of computers that Commodore sold in Europe. The Commodore 128 could also emulate in hardware a Commodore 64. As such it could use all of the peripherals from the Commodore 64. Lastly the 128 had a Zilog z80 coprocessor and could run CP/M. Along with the 1571 floppy drive, it could even share data with a variety of other CP/M machines.
For the most part, people used the Commodore 128's as Commodore 64's, as few vendors felt the need to write for the 128, when the 64 emulation was so good, they could keep selling to all segments. However there were special versions of Geos, and some Infocom games that took advantage of the higher resolutions & memory that were available to the 128.
Misc
The Commodore 128 was replaced by the Amiga line of computers.
