Audiation is like being able to hear music even when there is no music playing. It's like having a song stuck in your head that you can hear even though nobody else can hear it. When we audiate, we use our imagination to hear music in our minds, even if there is nothing actually making sound.
Just like when we imagine seeing things in our mind's eye, audiation is when we imagine hearing things in our mind's ear. This skill is really important for musicians because it helps them learn and understand music better. When someone can audiate a piece of music, they can hear it in their mind as they read the notes on a page. They can also use audiation to practice playing their instrument by imagining the notes being played as they practice.
Audiation is something that we all do naturally, but musicians practice and develop their skills with it so that they can use it to make their music even better.