Cloud Run functions, formerly Google Cloud Functions, is a FaaS (function as a service) product of Google Cloud. In FaaS, a developer uploads single-purpose functions and the provider runs them on demand, with no servers for the developer to manage. Google renamed Cloud Functions to Cloud Run functions, and functions are deployed in Cloud Run, a serverless platform of Google Cloud.
A function is either an HTTP function, which any web, mobile or backend application calls through its address, or a CloudEvent function, which runs when an event arrives from a Google Cloud service such as Cloud Storage, Pub/Sub or Firestore, or from Firebase. Google starts instances when events arrive, scales them with the load and stops them when no work is left. The open-source Functions Framework runs the same functions on a local machine, on premises, or on other Knative-based serverless platforms, and Cloud Trace shows how each request behaved.
Billing is pay per use: execution time is metered to the nearest 100 milliseconds, the number of invocations is counted, and an idle function costs nothing. A monthly free tier applies.