Caveat. I have about one day's experience with nostr. I am no expert. It is a framework upon which clients can be built. You can "log in" to any with your own keys, create many profiles with new keys, or don't "log in" at all. To date, I have found clients that mimic Twitter and reddit, and some clients include a lightning wallet with your keys. It's pretty primitive right now, but Jack Dorsey's development donation has created excitement. Decentralized commerce through lightning seems inevitable down the road.