Can you kind of explain trichotillomania to me?

Ok so in the past I've wondered if I had trichotillomania (urge to continually pullout body hair) when I was really young I would always pull out my eyebrows and lashes and my arm hair. I can control it better now, but it's weird. Anyways, I was in class and the kid down the row from me was leaning his head to his hand and was pulling at his eyebrows. I thought it was just a twitch and he was concentrating but then he started pulling the hair out at the base of his neck, on his jaw and back to his eyebrows. Now that I've noticed it he does it a lot, and it reminds me of me. I do that too and I was wondering what triggers it and why I've started in the first place. Or do you think he has trichotillomania? Do people normally just do that some times. I don't know please elaborate
Can you kind of explain trichotillomania to me?
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