PC-10: A full AT-sized model with 8088, combined Hercules/CGA/Plantronics Colorplus graphics provided by an ATI Graphics Solution card. Two variations were produced: the PC10-1, with one floppy drive and 512 kB RAM; and the PC10-2 with two floppy drives and the full complement of 640 kB RAM. The systems can be upgraded with the 8087 FPU.
PC-20: A PC-10 with a 20 MB hard disk
Colt: A rebranded PC10-III
Source: Wikipedia, "Commodore PC compatible systems", available under the CC-BY-SA License.
The Commodore PC compatible systems are a range of IBM PC compatible personal computers introduced in 1984 by home computer manufacturer Commodore Business Machines.
Incompatible with Commodore's prior Commodore 64 and Amiga architectures, they were generally regarded as good, serviceable workhorse PCs with nothing spectacular about them, but the well-established Commodore name was seen as a competitive asset.
Source: Wikipedia, "Commodore PC compatible systems", available under the CC-BY-SA License.
User summary
The PC-10 and PC-20 ranges are more or less identically, with the PC-20 originally being a cost reduced version of the PC-10. Each version have several revisions, but common for them all are the following specs:
IBM XT compatible
Intel 8088 CPU @4.77 to 9.54 MHz (adjustable on the fly using keystrokes)
640 kB RAM
ATI Graphics Solution card
and was expandable through ISA ports
Other IBM compatible machines were made by Commodore using 80286 and 80386 CPU.