A doorbell with intercom has a speaker to communicate remotely with visitors. You don't have to open the door immediately, because you first ask who is at the door. Some intercoms have a screen. With these video intercoms, you can also see who is at the door and you have direct contact thanks to the talk-back function. Smart doorbells always have an intercom function to see who rang the doorbell in the smartphone app and communicates with the person.