The 6502 processor appeared in 1975. It was the first 65xx processor. It was cheap.

The 6502 took many roles. Apple put a 6502 into many Apple II computers (but put a 65816 into each Apple II GS). Some 6502 hackers start with the Apple II.

ROM hackers know the 6502 as the central processor in the Atari systems (2600 through 7800) and in the NES. Some 6502 hackers start with the NES.

There is so much else to say about the 6502.