In one sentence
A brand entity is the structured, machine-readable identity of a brand: its name, category, products, people, locations and relationships, consistently expressed across its own site and third-party sources so that AI systems recognise it as one thing.
Models answer from entities, not strings. If your site says one thing, your LinkedIn says another and a directory listing says a third, the model has three weak signals instead of one strong one, and it will often prefer a competitor it can describe confidently.
The practical work is unglamorous: one canonical description reused everywhere, Organization structured data with a stable identifier, consistent naming of products, and enough independent third-party mentions for the model to corroborate.
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