Ok, it's an oauth2 login flow. When you "Login with Google/Apple/Github/..." it uses the protocol Oauth2.

Instead of having Google/Apple/... as source of identity, nostr can be this source of identity. It's "Login with Nostr" protocol for traditional websites (TIDAL could uses this for example)

nostr:note15pqc5nyqln7t6zgt063wl2jpz9apakk8ds7w2t2tp3p9qwcd0y6q75d32g