Amber alert?

Angelina • 26. 9 years w/ my love. Married 💍 I'm an artist, nature lover, Crystal collector, mommy to 2 doggies and our babies, Lilliana 5/26/16 & Elena 5/10/19
Sorry if this is a dumb question but can someone explain to me about amber alerts. I just got a text message about one that in my state but not anywhere near me at all. How do these things get sent to me. Is it like through the phone companies. They're just required to send them out to everyone? Or what? I've never gotten one before so it confused me a little