Used nostr without much idea about itself, but using Amethyst, it was the easiest i ever created account ever in my life
The working involves relays ( which reminded me of tor ) which helps messages pass from you to others and from them to you.
Discovering accounts can be through their public key or as usual, their username ( if set ). Its usable with just the key generated during our signup.
The downside is not much active communities and users other than mainly crypto enthusiasts, but people are increasing.