Ardour uses the JACK Audio Connection Kit. You should install JACK before installing Ardour. Follow the instructions in Section 2.3.1, “Install and Configure JACK” to install JACK.
You need an audio interface to use Ardour. If you will record audio with Ardour, you must have at least one microphone connected to your audio interface. You do not need a microphone to record audio signals from other JACK-aware programs like FluidSynth and SuperCollider.