Complex sentence: A personalized gun, or smart gun, is a firearm that only fires when activated by an authorized user, in order to prevent misuse, accidental shootings, gun thefts, use of the weapon against the owner, and self-harm.
Split into simpler sentences: A personalized gun, or smart gun, is a firearm that includes a safety feature or features that allow it to fire only when activated by an authorized user. These safety features can prevent misuse, accidental shootings, gun thefts, use of the weapon against the owner, and self-harm.