About cards in flows
Each card represents one specific step in a flow. Within a card, there are two types of fields: input and output. Input fields accept values. Output fields are values that a card produces which can be used by subsequent cards. The ability for an Action card to accept input, and then return a different output, is one of the most powerful features of Workflows.
You cannot use the input and output fields of an application's Action card unless you've already set up a connection to that card's third-party application and selected options, if any.
Input fields accept values. These values determine how an App Action or Function will proceed. For instance, for a Send Email card, there are input fields for To:, Subject: and Message Body. For a Replace function, there are input fields for the text to look in, the text to look for, and the text to replace.
Output fields are assigned values after an Event, Action or Function runs. For instance, for the Replace function there’s an output that has the new text value after the replacements are made. For a Salesforce New Record event, there’s an output for the id of the newly created record.
A powerful feature of flows is the ability to map the output field from one step to the input field of another step. For example, you can drag an email name output from a Read Customer action and drop it into the input field of a Send Email action. Every time the flow runs, the email from that specific customer will be used as the address to which an email will be sent.
Chain together multiple cards and map outputs to inputs to build flows that transform data, use logic to decide on next steps, and take actions using that data.
Additional options in cards
Along the bottom of each card, there is a set of buttons with available options:
Help: The "?" icon. Provides a help topic specific to that card.
Test This Card: (for action and function cards only) Allows you to provide sample input values and see the resulting output.
Run When: (for application event cards only) Let's you set your event to trigger once for all new records (rather than once for each record) or trigger only when no records are found. See Set options to poll for data.
Schedule Options: (for non-webhook application and schedule events only) Controls how often to check for new data or run the flow.
Endpoint Settings: (for API Endpoint event cards only) Allows you to choose a security level and provides the URL for invoking the endpoint.
Filter Fields: Useful for cards that have many fields, such as a Salesforce record that could have hundreds. Lets you filter the view to only show fields that match the text you type.
Additionally, there is a gear button at the bottom-right with Other Options:
Edit card: When in customize mode, you can rename the card (great for documentation) and rename or reorder fields. See Customize a card.
Choose fields : Allows you to turn on or off fields that appear on the card. This is useful for cards that have many fields, possibly hundreds, where you only need access to some of them.
Error handling: Gives access to error options such as automatic retry or running an error handling flow when the card fails. See Set error handling for cards in flows.