A project in DEX is a self-contained file that contains all the details for your design. It does not rely on any external files (except font files). All schematics, text sheets and the PCB for your design is contained in this single file.
Your design project consists of one or more schematic diagrams and a single PCB.
The schematics are the logical design for your project. The PCB is the physical manifestation of your design.
A Schematic
The PCB (2D Layout)
The 3D PCB without parts
The 3D PCB with parts