How do you differentiate between your friends, your family, your lovers, and your hated enemies?
Sound? Body shape?
Of course, these are also a way to distinguish them. However, you must know that there are many strange people in the world, and there are many people with similar voices and body shapes!
Then, apart from voice and body shape, is there any way to distinguish them?
Face!
That's right! Face is the best ID of a person's identity! There cannot be two identical leaves in the world! Even twins have slightly different faces!