that is amber alert?

An AMBER Alert or a Child Abduction Emergency (SAME code: CAE) is a child abduction alert bulletin in several countries throughout the world, issued upon the suspected abduction of a child, since 1996.
AMBER is officially a backronym for "America's Missing: Broadcasting Emergency Response" but was originally named for Amber Hagerman, a 9-year-old child who was abducted and murdered in Arlington, Texas in 1996.

Alternate alert names are used in Georgia, where it is called "Levi's Call"(named after Levi Frady); Hawaii, where it is called a "Maile Amber Alert" (named after Maile Gilbert); and Arkansas, where it is called a "Morgan Nick Amber Alert" (in memory of Morgan Chauntel Nick).

Frady, Gilbert and Nick were all children who went missing in those U.S. states.
AMBER Alerts are distributed via commercial radio stations, internet radio, satellite radio, television stations, and cable TV by the Emergency Alert System and NOAA Weather Radio (where they are termed "Child Abduction Emergency" or "Amber Alerts"). The alerts are also issued via e-mail, electronic traffic-condition signs, the LED billboards which are located outside of newer Walgreens locations, along with the LED/LCD signs of billboard companies such as Clear Channel Outdoor, CBS Outdoor and Lamar, or through wireless device SMS text messages. AMBER Alert has also teamed up with Google and Facebook to relay information regarding an AMBER Alert to an ever growing demographic.
By/ Wikipedia