A common data model folder or CDM folder is a folder in a Data Lake that contains a model.json file. This model.json file describes the schema and location of the data. Since the model.json file follows a well-defined schema, it facilitates metadata discovery and interoperability across applications.
The following screenshot shows an example CDM folder stored in Azure Data Lake Storage:
As shown in the preceding screenshot, Dataflow 1 is the CDM folder as it contains a model.json file that describes the shape/schema and location of the data files.
To learn more about the CDM folder, follow the Microsoft documentation page at https://docs.microsoft.com/en-us/common-data-model/data-lake.