A car alarm is a security device designed to deter theft and vandalism. It typically consists of sensors that detect unauthorized entry or movement, triggering a loud siren or alarm sound. Many modern car alarms also include features like remote keyless entry and immobilizers, which prevent the engine from starting without the correct key or fob. When activated, a car alarm can alert the owner and nearby individuals to potential threats. Some systems can send notifications to a smartphone, allowing the owner to monitor their vehicle's security in real-time. Overall, car alarms are an important tool for protecting vehicles from theft and damage.