matrix on Nostr: what‘s #nostr ?

{ "id": "1568cc974de396588444aba5c3c296e6814daa831096ddd43f4527be6d9c130d", "pubkey": "c3be42223cdf9cc21f7823d2566589e5c2ce7e003dafeed9c6f318a3c7c45f54", "created_at": 1675349910, "kind": 1, "tags": [ [ "t", "nostr" ] ], "content": "what‘s #nostr ?", "sig": "c7c7e445814014d6f202b910bee667869e3263e28eaa888ed0ab09a8ab15b89e3d48327855a1e1778849e19fc1f20e152fa83abd231bac58e45d500bf98a5128" }