Cloud Storage
Every Node application on Cloudnode runs in a virtual machine with its own disk storage. The disk holds a full checkout of the application's Git repository. So you have access to modules sub-modules and static resources, you have checked in. The disk also holds all Node modules you have installed using the npm command and a minimum set of directories to get Linux running like /etc.
Special Directories
You should not assume, that there is write access to the disk except to the /mnt and /tmp directories. Your application can use these directories to store dynamic data. As the names suggest, /tmp can be used to store volatile files and /mnt can be used to store permanent files. These will always "follow" your application and be mounted at /mnt.