Yep, every AI call is essentially just asking it to predict what the next word is after:

  <system>
  You are a helpful assistant.
  </system>
  <user>
  Why is the sky blue?
  </user>
  <assistant>
  Because of Rayleigh scattering. The blue light refracts more.
  </assistant>
  <user>
  Why is it red at sunset then?
  </user>
  <assistant>

And we keep repeating that until the next word is `</assistant>`, then extract the bit in between the last assistant tags, and return it. The AI has been trained to look at `<user>` differently to `<system>`, but they're not physically different.

It's all prompt, it can all be engineered. Hell, you can even get a long way by pre-filling the start of the Assistant response. Usually works better than a system message. That's prompt engineering too.