A baby monitor is a device that allows parents to listen to or watch their baby from another room. It typically consists of a transmitter unit placed near the baby and a receiver unit that parents can carry around. Some monitors also include video capabilities, enabling parents to see their baby as well as hear them. Modern baby monitors often come with additional features such as temperature sensors, night vision, and two-way communication, allowing parents to talk to their baby. They can connect via Wi-Fi or use traditional radio frequencies, providing flexibility in how parents monitor their child's safety and comfort.