I don't want to be mean, but this post has exactly the problem the person you're replying to was complaining about. The person you're replying to, I think, would like an explanation that reads more like "It's like Twitter, but not tied to a mega-corp, just for you and your pals". I don't know if that description actually fits Nostr though because, like the person you're replying to, I have a pretty hard time understanding what Nostr actually _is_.
My point is that question is sort of a category error. It's like asking what type of business the internet is for, or what the use case of smart phones is.
Here are a few things built on nostr, with specific use cases:
primal.net is a twitter-like client with bitcoin micropayments and long-form articles (also see coracle.social, nosotros.app, jumble.social, Amethyst, Damus, yakihonne.com and many others);
zap.stream is a twitch-like client for live streaming;
flotilla.social and chachi.chat are group chat clients;
dtan.xyz is a client for torrenting on nostr;
satlantis.io is sort of a travel ratings thing;
zap.cooking is a recipe website;
yakbak.app is for voice messages;
nutstash.app is a cashu wallet built on nostr;
cashumints.space lists cashu mints that advertise themselves on nostr.
What's neat is that all these clients can do things the way they want to, but remain interoperable, which means that new developers can create an app and immediately have access to all existing nostr users and their social graph.
>It can be used to some extent via a browser using web clients, but it's best used alongside extensions for authentication and key management
Just wonder can the key just sit in the IndexDB? And it is decrypted on the client side (when user enters password to decrypt the key) to sign a message to send to peers or relay, they can verify your identity by checking against the corresponding public key.
The question isnt a category error and deserves a direct answer.
If I follow what you're saying the answer could have been: "it's a framework/set of protocols for building a Twitter that can show all the stuff on other compatible Google+/Facebooks"
If you have a preference for this style of definition, then we could say that
Nostr is a protocol that's well suited for creating decentralized applications that need publicly verifiable identity, censorship resistance and event based communication.
For example, https://zapstore.dev/app is an Android AppStore that uses nostr to provide a decentralized way to verify the developers and remove "fake" apps.
