One of the most feature-rich clients is Nostrudel - https://nostrudel.ninja

It's better suited for tech-savvy users, but it offers an opportunity to dive into the features of the Nostr protocol.

Here’s one of the brief FAQs on Nostr:

nostr:naddr1qvzqqqr4gupzqx78pgq53vlnzmdr8l3u38eru0n3438lnxqz0mr39wg9e5j0dfq3qqxnzdesxs6njd3ex56rgvpjgcx5k9