TL;DRThe named thing being counted — API calls, gigabytes, active seats — that a product's price refers to.
A meter is defined once in the catalog and referenced by products and templates. A usage meter aggregates events; a seat meter tracks a running balance per customer.
Templates map a column or a formula in the source file to a meter, so the same meter can be fed from a CSV one month and a database sync the next.
Where it happens in Sonic
Next
See it on your contracts
A walkthrough on the agreements and files you actually bill from — not a slide deck.