Concept
HTTP Callout pulls or sends data between the flow and an external system via Flow Builder without using code. You can set up direct integrations as needed without having to work with a developer or call a middleware tool. After you configure the HTTP callout action in a flow, Flow Builder auto-generates an external service registration, an invocable action, and Apex classes that you can use to create an Apex-defined resource for flows. You can then use the data output of the API request as input within Flow Builder and across Salesforce.