ANSWER

What kind of robot do you mean? There are a lot of them.

Is it mobile or not? What must your robot do?

If it is mobile, f.e. robot vacuum-cleaner it has:

- central processor

- chassis (wheels)

- sensors (to detect walls, furniture etc)

- vacuum cleaner

If it is not mobile, f.e. welding robot on cars plant it has:

- central processor

- video camera ("eyes") or some other kind of sensors

- manipulator with the welding device

If you mean the humanoid robot the things are more sophisticated

- power central processor (brain)

- eyes

- ears

- speaker

- arms

- legs

and so on