nobody on Nostr: Whats a block?

{ "id": "3f55d26f4cfa16a5f873a959ba839276796d68c99a622d33af8c839880ae6fdc", "pubkey": "0259247de23ef81418dd2bd2f13697451af2af4f873098af989051bbbd5014d3", "created_at": 1696013087, "kind": 1, "tags": [ [ "e", "77a384265aa73eac96b9f4afe785f565a2e4bf6d74377e4eef608b34791ab70d" ], [ "p", "ab74910c7015f6b98a25e29e5563764e4351fc2c1ea5e4093973a4e0ff584d63" ] ], "content": "Whats a block?", "sig": "ae41a2eff198e561bbe7a51d05098980966308b291e5f79a8dcabbb9ec9909eafeeb5f032875503fa21bf4509e33bdd2190238e3bd3bbf78b342597c8367a82b" }