The intercom is an easy connection with the people who came to you, whether it is delivery, or just someone you do not know came to your door. After pressing the call, a message will come to your phone and you will be able to talk to the person standing at the front door. If you missed this call, or were busy at the time, you can watch the video and see who came to you.
An intercom is a two-way video link that replaces a simple call and notifies you even when you are not at home.