Core Concepts

This section covers the three concepts you should understand before designing your own workflows.

• How a Workflow Runs: the lifecycle of an instance, instance and step statuses, retries, and livemode isolation.
• Variables and Expressions: the ${...} template syntax, the four reference forms, and the monetary helper functions used inside compute steps.
• Validation and Errors: when validation runs, what the error envelope looks like, and how to read field-path errors.

If you have not yet created your first workflow, start with the Quickstart.