The commodore PET line of personal computers was introduced in 1977. It uses the MOS 6502 CPU, runs commodore Basic in ROM, and has built in keyboard, monitor and in the early models a cassette recorder.

The Commodore PET 2001 was the first model of the series. The CPU controlled the screen, keyboard, cassette recorder and any peripheral that was connected.

Commodore was the first company to license Microsoft's 6502 BASIC. The agreement with Microsoft stated that Commodore would only pay for the license upon shipment of the PET. This almost bankrupted Microsoft. Microsoft was saved by Apple's decision to also license Microsoft's BASIC for their Apple II computers.

Source: WikiPedia - Commodore PET

The 6502 is an 8-bit MicroProcessor designed by MOS Technology. The team was led by Chuck Peddle and had also worked on the Motorola 6800. The 6502 is a simplified, but faster and cheaper design than the 6800.

The 6502 was introduced in 1975 and was the cheapest microprocessor on the market. Together with the Zilog Z80, the 6502 helped start the home computer revolution of the 1980s. The 6502 was used in a wide range of devices: the Atari 2600, the 8-bit Atari home computers, the Apple II, the Nintendo Entertainment System, the Commodore 64, the BBC Micro and many others. All used the 6502 or a variation of it.

The 6502 is a 1MHz design, while the 6502A is designed for 2MHz. The 6502A is 100% compatible with the original 6502.

Commodore soon bought MOS Technology, but conitnued to sell the microprocessor to competitors and licensed the design to other manufacturers.

Source: WikiPedia - MOS Technology 6502