https://docs.ordinals.com/

It’s a shared hallucination based on numerology. It has no explicit meaning to bitcoin at the protocol level. This is separate from inscriptions which is putting data onto the blockchain. Combined you get NFTs and BRC-20 and whatnot. Imho, ordinals as a concept in numerology is interesting but tying them to inscriptions for JPEGs is meh at best. Ordinal theory can never go away, even if JPEGs stop being inscribed.