Voice is personality - if not yours, then your narrator’s or your POV character’s.
Voice can’t be learned, but it can be refined. The more you write, the clearer it will become.
Voice is filled with bias and nuance.
Voice is colourful.
Voice is what makes your story different from mine when we are describing the same incident.
Write until you find it, because voice is what makes you unique.
And speaking of voices, here is one I could listen to all day: