A data source connector is a piece of code that runs on Lambda that translates between your target data source and Athena. When you use a data source connector to register a data store with Athena, you can run SQL queries on federated data stores. When a query runs on a federated source, Athena calls the Lambda function and tasks it with running the parts of your query that are specific to the federated source. To learn more, review the Amazon Athena User Guide: Using Amazon Athena Federated Query.