fro on Nostr: whats a block list?

{ "id": "47433ea855ac53ac19b6c1536af9514619b854ec01ee6a237f33bd543ca59be9", "pubkey": "08ccd539f9e4c21425d31942169a256ef19cabeb10fb199f054011d04e9a108b", "created_at": 1672670662, "kind": 1, "tags": [ [ "e", "b6e850887ac0e7a14240d6b557b6ca089e81e331745ca31a56fc2763fb5db63a" ], [ "p", "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245" ] ], "content": "whats a block list?", "sig": "f021f17be7943a0ce9dff5fef5af310b999d59d309344f0549a4557a6d8b8d9565cb1c50b3d0701b7ecf4635f19665458a613d4c5bb4eaf5ddce1816b8414223" }