The 6502 does not place any hard constraints, or meaning to any of the memory locations in the CPU. The Apple II uses the following map:

(from http://apple2history.org/history/ah03.html)

Page $00: used by the 6502 processor for storage of information that it can access quickly. This is prime real-estate that is seldom available for general use by programmers without special care. Page $01: used by the 6502 for internal operations as a "stack." Page $02: used by the Apple II firmware as an input buffer when using the keyboard from BASIC, or when a program uses any of the firmware input routines. Page $03: general storage area, up to the top three rows (from $3D0 through $3FF) which are used by the disk operating system and the firmware for pointers to internal routines. Pages $04-$07: used for the 40 column text screen. Pages $08-$BF: available for use by programs, operating systems, and for hi-res graphics. Within this space, Woz designated pages $08-$0A as a secondary text and lo-res graphics page (although it was not easy to directly use, as the firmware did not support it), pages $20-$3F for hi-res "page" one, and pages $40-$5F for hi-res "page" two. Page $C0: internal I/O and softswitches Pages $C1-$C7: ROM assigned to each of the seven peripheral cards Pages $C8-$CF: switchable ROM available for each of the seven cards Pages $D0-$D7: empty ROM socket #1 Pages $D8-$DF: empty ROM socket #2 Pages $E0-$F7: Integer BASIC ROM Pages $F8-$FF: Monitor ROM