You know the small pin like that sticks out of the tyre sidewalls, that one is the tyre indicator right?

Am wondering how it works, how does it get shorter as tyre wears out? It gets shorter based on number of years or based on tyre wear? How does it work?

I though the side wall near the edge got like hair like thing sticking out, that is not indicator? I see new tyre that thing quite long.

Can show picture?

How the sidewall triagle wear off since it's not under friction? Is it more of a date indication rather than wear indication?