The 6502 microprocessor and it's variants was a popular model of microprocessor from the mid 1970's to the early to mid 1990's. It powered the Commodore 64, Atari 2600, the Apple II, and the Nintendo Entertainment System.
The 6502 microprocessor is an 8-bit microprocessor but has a 16-bit addressing scheme and thus has memory addresses from $0000 to $FFFF.
|$0000 to $00FF||zero page, used in one byte memory addressing using zero page addressing.|
|$0100 to $01FF||the stack, used to store return addresses|
The 6502 is a little endian microprocessor. That is, it stores the least significant byte before the most significant byte.