How do those door cameras (e.g., Ring) work? Do they require a smartphone?

I would like the added home security of a camera and doorbell response system, but first I want to understand how it works at my end. Does it involve
• smartphone
• Alexa/Siri software
• QRC codes
• phone apps
• special wiring
• etc.?

Please share the basics and if possible give me some guidance on how to choose one system over another. I don’t know anything about them.

I really don’t want my phone to pester me whenever someone is at my door, but I would like to be able to review video when there’s been suspicious activity. I guess that means a motion-activated device?

Thank you.
 
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