Imports are used to insert data into an application. Like Exports, Imports can run standalone, or in the context of a Flow.
Standalone Imports are useful for integrations where user actions (like clicking a button) need to invoke an application's API in real-time and return the results immediately. Standalone imports are especially useful for applications that need to integrate with more than one other applications, and/or applications where the development environment is less than ideal and writing native API client code would be counter productive. Celigo uses standalone Imports extensively in it's spreadsheet and email sync products.
Imports running in the context of a Flow will also execute synchronously but will channel results back to the flow so that stats can be reported in a job record.