Every place in Google's Geotargets dataset has a criteria ID — a stable integer that identifies it uniquely. Where the canonical name is the human-readable label, the criteria ID is the compact key.
It is handy for tooling: a shareable comparison link, for example, can carry a couple of criteria IDs instead of long encoded names and resolve them back to full locations on the server.
See how Criteria ID changes real results: compare Google from any two locations.