Your client system's data gets to a Starter Kit instance via the Ed-Fi ODS platform's API. The Ed-Fi API uses standard REST conventions and JSON as its data format.
A REST API is a common pattern in software development. If you are not familiar with this pattern, we recommend these resources:
The entire Ed-Fi ODS / API is extensive, but client applications typically only interact with a few of these API resources. Those specific resources are covered in the section Data Requirements.