NES components

CPU

central processing unit. its the brains of this computer. it has 2 kilobytes of memory with 256 bytes allocated to the stack pointer.

PPU

picture processing unit. or a GPU. it handles the graphics The NES GPU. unlike modern GPU's it uses no linear algebra or parallelization it has no instructions. but you communicate to it by reading/writing to 0x2000-0x2007

APU

the apu is a physical component and memory mapped device that handles Sound. you write to 0x4000-0x4017

ROM

ROM or read only memory, is were the binary is stored to be executed. the NES rom is mapped between 0x8000-0xffff. the ROM also contains CHR which is used to render graphics

on the physical NES the ROM usually comes with a Lock-out chip. which is a chip that matches electrical signals to prevent people from writting non Nintendo approved NES games. this is necessary because the Atari flopped because people writting low quality games for the system. crashed the entire video game market.

Controllers

the joy pads or input. is also a memory mapped device and physical component it works by reading from 0x4016/0x4017. when the strobe bit is set.

0x4016 is for player 1

0x4017 is for player 2

Bus

the bus is how all these components communicate.
there is an address bus and a data bus. addresses can get up to 16 bits.