A project file is an XML file which stores all settings of a particular project. You should save a project file for each project and back it up. You will NOT be able to create a project file backwardly from the generated app later.
A project file is an XML file, like other XML document, it is human-legible. You should be able to open a project file in any text editor and view the content. Each object (e.g. database, table, field, etc) is represented by an XML node in the project file. The object properties are saved as attributes of the node.
A project file is in utf-8 encoding, your text editor needs to support utf-8. Most text editors support utf-8 nowadays. You can simply use Notepad if you do not have other text editors. With basic understanding of XML, you can change the settings manually. However, If you modify a project file, make sure your keep it well-formed. To check if the file is well-formed, you can change the file extension to .xml and open it with a browser. If the file can be loaded and displayed properly in the browser, it is well-formed.
DB AppMaker supports auto-backup. When you save a project, the old version will be saved to the subfolder <Documents folder>\<product name>\Backup folder first, you can recover older versions of your project from the backup folder in case of corrupted projects or other accidental losses. Note that only the latest 10 versions will be kept, older versions will be deleted.
Each project has a project name. By default the file name (without extension) of the project file is used as project name. Before you name your project file when saving it for the first time, a temporary name, Project<n>, where n is a number, is used. The project name is an important property, it is used in the generated app to identify your project. If you need to change the project name, use Advanced Settings.
Save As vs. Save A Copy
If you want to create a new project based on an existing project, use [Save As...] under the [Project] menu. If [Save As...] is used, the project name are changed in the new file. The new file is NOT the same project anymore.
If you want to create a backup copy or another version of an existing project only, you should use [Save a Copy...] to save the file with another name. If [Save a Copy...] is used, the project name are NOT changed. The project name may not be same as the file name anymore. However, with the same project name, apps generated from these project files will still work like they are generated from the same project file.