Everyone's larynx grows during puberty, but a girl's larynx doesn't grow as much as a boy's does. That's why boys have Adam's apples. Most girls don't have Adam's apples, but some do.
The Adam's apple, in relation with the thyroid cartilage which forms it, helps protect the walls and the frontal part of the larynx, including the vocal cords (which are located directly behind it). Another function of the Adam's apple is related to the deepening of the voice.
I didn't know that. I have a massive Adam's apple and a very deep voice. I sing bass and can hit some loooow notes.
In high school, we had to wear dress shirts and ties. I used to show off by making my Adams apple jump up and down which caused my buttoned dress shirt and entire tie below it, snug around my neck to bounce up and down by a couple inches.