What is the difference between an RCA jack and a digital audio coaxial jack?
Physically, there is none. the difference is in the signal it passes.
RCA plugs and jacks are used for a myriad of different things in the real world.
Sometimes it's color is a clue.
Yellow generally means composite video.
Red, blue and green are RGB component video signals.
Orange is digital audio.
Red and white are line level audio signals.
...and the list goes on and on. YMMV