No modern recording studio can exist without an audio interface. This is the central control room where all your audio magic is made.
Whether you have a home studio or a huge professional enterprise, your audio interface is the crucial mechanism that carries sound from the real world (from your instruments or microphones), inside your computer, and back out again.
Digital recording and processing is only possible thanks to audio interfaces. That’s why these are the number one most important pieces of equipment any audio engineer can own.