What is this on my teeth?

im 12 and my teeth well tooth the left one of the two ones in the front theres a white spot on it i went to the dentists they said it would grow out as i get older but they dident say what the ehck it is
does anyone know Additional Details1 month agooh and my teeth are white but the spots are just whiter and ive never had braces and all in all theyre perfect
--------------------------------------------

It could be calcification - the start of a cavity, but instead of decaying it got hard again. It could also just be a defect in the tooth. Either way if you're curious you should ask the dentist what it is. Normally checkups are every six months. Next time just ask him. But make sure to keep that are really clean, any time there is something wrong with the enamel it can decay really easy and that is not a good place to get a cavity. Good luck!