Core Project Files
The files that make up Core games are all stored locally on the computer where they are created. Because of the way Core builds all games out of assets downloaded with the Core installation, they are also quite small files, that can be found by default in the My Games > Core (it may be CORE) > Maps folder.
Essential Files of a Core Game Project
In the game file directory, two folders determine the way the project is built, Tree and Asset Manifest. They contain the essential blueprints of what objects are needed and where they should be to build up the game using these definitions. They can be found in the Data folder of the project.
Tree
The Tree folder contains a file called Tree.pbt which essentially lists every single object in the Hierarchy, and all the properties of each object found in the Properties window, like materials, transforms, visibility and lifespans. The tree will only list a property that is different from the default values.
AssetManifest
The AssetManifest.pbt file in the Tree folder is a list of all CoreObjects and Materials that are used in the Hierarchy.
You can think of AssetManifest as a list of parts, and Tree as instructions on how to build them into the game.
Folders
Folders exist to partition the project into smaller sub-trees, to keep every single object of the project from being listed as a single file. By contrast, Groups exist to organize models and make their parts able to scale uniformly together. In the Tree.pbt file, both are listed as a "Folder", but the objects called "Folder" in the Hierarchy are special types with the property IsFilePartition marked as true.
Each Folder created in a project creates an actual folder inside the Tree folder, each of which includes its own AssetManifest.pbt and Tree.pbt files, listing the asset references and property data for the objects in the Folder in the Hierarchy.
Using Folders to partition workspaces for each collaborator on a project will prevent merge conflicts in the Tree.pbt file. See the GitHub Tutorial for more information.
Templates
Templates are stored in a separate location from the Tree and AssetManifest files, which you can find in Data > Templates. Each template is a single .pbt file that lists both the required objects and what their properties should be to build up the template. When templates are added to the Hierarchy, they are listed in the Tree.pbt file as a TemplateInstance, with any changed properties listed, just like a CoreObject.
When a template in the Hierarchy is deinstanced, it stops being listed as a TemplateInstance and instead adds the tree of objects and properties needed to build it directly to the Tree.pbt file.
Community Content
Community Content imported in a project or published is added to a Community Content folder in the main project folder, which lists all the templates and scripts used in the Community Content piece, as well as a FolderMeta.pbt file that lists the author and description, covering the information found in the listing where it is published.
Once Community Content is added to a project by double clicking it from the Core Content window and dragging it into the Hierarchy**, it will appear in the Imported Content section of the Project Content window, and the template folder will be added to the Data > Subfolders folder in the project files.
Learn More
Templates | GitHub Tutorial | Community Content | Backing Up a Project