What it means
Most content systems invent a model of their own that nobody outside them understands. Loam borrows the one the web already agrees on. An article is an Article with a headline and an author. A business is an Organization with an address. An event is an Event with a startDate.
Not as an export, not as an option: the record is the content. The page, the machine views and your agent's understanding all turn around it.
How loam does it
Loam adds mechanics, never vocabulary. An entity has an identifier. Entities point at each other with small references that resolve when the page is read. An entity with a slug is a page. Each type asks for a handful of required fields.
The engine guards those mechanics — a reference to nothing, a missing required field, a file that does not parse — and never polices meaning. It will not tell you your Service should really be a Product.
Because the fields that render the page are the same fields that feed the structured data, the machine view can only claim what the page shows.
What it costs
Schema.org has awkward words for some things. The rule: keep the public term where the mechanics do not care, and add a small render-only field where the page needs something the vocabulary lacks — stripped from the machine view so the claim stays true. A moment of thought per type, against a private language every reader would pay for, forever.