A plain folder that you own and keep in your own repository. models/ holds the transformations, pipelines/ holds the pipelines built from templates, tests/ holds the golden test fixtures and expected outputs, and emolysis.yml names the target platform.
Each project also keeps a local lakehouse for samples, which is not meant to be committed. Credentials are never written to the project; they live in your machine's credential store.
The layout is familiar to anyone who has used a SQL modeling tool. Projects and emolysis.yml describes each file, and the quickstart walks through a first session from an empty folder to a deployed pipeline.