The commodore 64 is, along with the Apple II and the Atari XL computers, the most famous home computer. According to the 2001 edition of Guinness book of records, the C64 was the most "prolific computing device ever manufactured". During its production run from 1982 to... 1993, about 30 million (!) units were sold. To put this number in perspective, that's more than all the Macintoshes in the world.
The C64 was an up-market version of the VIC-20. A wide range of software packages, games and programming languages was available for this machine which was itself available practically anywhere from a toyshop to a business supplier.
Superficially, the C64 closely resembled the VIC-20. It had the same casing, an identical keyboard configuration and virtually the same interfaces and sockets. But the apparent similarity belies some fundamental differences: a MOS 6510 processor and 64 KB of RAM which was quite unusually large at the time for a model of this price range. The C64 also had the ability to recognize user-established priorities by which 'sprites' (or movable blocks) could move independently of displayed text/graphics, enabling the creation of graphics with up to 8 layers.