Data Sources
Data Sources allow you to populate a config variable dynamically after they enter some connection settings. This is handy because customers' configuration differs in third-party apps. Customers have different Facebook business names, different Google Analytics accounts, different fields on Salesforce resources, etc. You can pull in those things, and allow customers to choose their Slack channel, select a folder in Google Drive, map fields from Salesforce, etc.
If you would like to populate a config variable dynamically from a data source, first ensure that a connection config variable for the third-party app is present on your first config page. Those are generally automatically created when you add a step to your integration for that third-party. On a subsequent page, add your config variable. Under Data Source, select the component and data source that you would like to use (for example, the Slack Select Channel data source).
Your customers will authenticate with the third-party app on their first config page, and will see data dynamically loaded from the third-party populate the config variable.
Many public connectors contain data sources for common configuration tasks (like selecting a record from a dropdown menu). If you would like to build your own data sources, either using an existing public connector's connection, or adding a data source to your own custom connector, see Config Wizard Data Sources.