Screen Time includes computers/Chromebooks, cell phones, tablets and other mobile devices, and television.
Some helpful articles to read:
What do we really know about kids and screens? from the American Psychological Association
Screen Time and Children from the American Academy of Child and Adolescent Psychiatry
What Does Too Much Screen Time Do to Children’s Brains? from New York Presbyterian
Children and Screen Time: How Much is Too Much? from CableCompare.com
Screen Time vs. Lean Time Infographic from the Centers for Disease Control and Prevention (CDC)
Children and Adolescents and Digital Media from the American Academy of Pediatrics
Kids using screens more than recommended, new study finds from ABC News