How does a SNS work?

Excuse me, could you please explain in more detail how does a social networking service, or SNS, actually work? I understand it's a platform where people can connect and share information, but I'm curious about the technical aspects behind it. How are users able to create profiles, interact with each other, and share content like photos and videos? Is there a specific architecture or protocol that SNSs follow? And how do these services ensure the security and privacy of their users' data? I'd appreciate any insight you could provide.