Short & Simplified explanation of how Nostr actually Works:

First: Clients and Relays. Every person who uses the Nostr runs a client. Anyone can run a relay.

Each user is identified by a public key, and every post is signed. The clients check these signatures to make sure they are legitimate.

Clients get information from the relays they choose and share information with other relays they choose. Relays only communicate directly with users, not with other relays.

To "follow" someone, a user just tells their client to look for posts from that person's public key.

When a client starts up, it gets information from all the relays it knows for all the users it follows (like all the updates from the last day). It then shows this information to the user in chronological order.

People can post any kind of structured information, but the most popular types will become part of the standard, so all clients and relays can use them easily.