Nostr: What are NIPs, and why do they matter?

Short answer

NIPs are Nostr Improvement Proposals that document how clients and relays can implement shared features. NIP-01 describes the basic event and relay flow; other NIPs define optional behavior such as profiles, relays, messages, and zaps. A NIP's existence does not mean every app supports it. Check its status and both sides' implementation before promising that a feature will work.

Sources

Nostr Improvement Proposals index, NIP-01: Basic protocol.