Why will a car door not open from the outside when it is working inside?

A car door will not open from the outside when it is working inside because of the child safety lock function. This feature is included in most modern vehicles to prevent children from accidentally opening the doors while the car is in motion. When the child safety lock is engaged, the door can only be opened from the inside. To disengage the child safety lock, there is usually a small lever or button near the door handle.