Data Sources let you create and maintain logical data sets that can be used in Screens. A few examples are a list of choices, a product catalog, and a list of contacts.
You can use Data Sources in Choices questions across any number of Forms. Data Sources are also used as the backing data for other Screen types. As an example, you could have a Contacts data source which you expose as a "Listing" type screen. This would have its own icon on your app start screen.
Data Sources save time by centralizing your data sets in one place. They also automatically update any changes you make to any Screens to which that Data Source links. The platform will ensure that mobile app deployments of these linked Screens will also seamlessly update.
For even greater flexibility, technical users are able to integrate with other systems by using Data Source APIs (GET or PUT). Changes to database tables or lists stored in other systems can automatically update the mobile app. For example, if inventory software is where the catalog of products is maintained for your company, then changes to that catalog of products could automatically update in the mobile app, by using the Data Source API(s).
See also
Adding a New Data Source
Editing Settings and Rows
Using Image Columns