It's a file format used to store the design of a Lotus Notes database, including:
* Forms: The templates for how data is displayed and entered.
* Views: How data is organized and displayed in lists and tables.
* Agents: Automated tasks and processes.
* Other design elements: Navigation, security settings, etc.
The NTF file doesn't contain the actual data itself; it only stores the design structure. When a user creates a new database based on an NTF, the data is stored separately in a NSF (Notes Storage Facility) file.