Human identities are unique in our information outputs. Our vocabulary, our catchphrases, our curses or praise; our characteristic ways of typing, punctuation, spelling, speed, and many other markers, not all known, combine to form an unforgeable, dynamic, evolving personal identity far more unique than real world biomarkers like fingerprints or retinal blood patterns.

Our identities are the sum of these things, and are expressed in a spectrum physically emotionally and mentally. Rather like an aura.