A doorbell is a device that is attached to a doorbell button or button plate and is used to ring a bell. Doorbells are often used on the doors of houses, apartments, or buildings to let people know that someone is at the door. When someone presses the doorbell, the bell will ring and the person inside the building will be notified that someone is at the door. Doorbells are available in various styles and can be made of different materials such as metal, plastic, or wood. Some doorbells also have an intercom system so that the person inside the building can talk to the person at the door before the door is opened.