Share a contact, search a contact. Think of it as a shortcut to a nprofile (npubs + relays hints).
Thanks a lot. Need to ask about relay hints. In this context what would that be?
Tell people where you write your notes and where you would like to read replies. Aka Outbox (originally called "gossip") model. https://mikedilger.com/gossip-model/ This is the foundation of Nostr decentralised structure.