If you are new, the library’s quickstart is the shortest path from nothing to a first answer. If something looks broken, read Status first — it settles in seconds whether the problem is ours. If you are still deciding whether a panel suits your problem at all, the concept pages are written for exactly that, including the cases where the answer is no.
Plan terms and how a call is actually billed live in the library, on one page that owns those facts so that nothing else has to restate them and drift. What a plan costs is on pricing, deliberately kept top-level: it is a page people need to reach without navigating first. Developer documentation has its own door at the API.