One entity's series — a worked example of what the rows contain.

Deliberately a single entity rather than the whole feed: ~1,100 points per interval is the product for the price feeds, and a chart of all of them is unreadable anyway. Which column names an entity, which column to chart and its unit all come from the schema via hints_for; a feed with no entity at all (system demand, price adders) is simply its one series.

The node parameter keeps its name across every dataset — it means "the entity" — because the frontend already speaks it.