File represented by .ONE extension are created by Microsoft OneNote application. OneNote lets you gather information using the application as if you are using your draftpad for taking notes. OneNote files can contain different elements that can be placed at non-fixed locations on document pages. These elements may contain text, digitized handwriting, and objects copied from other applications including images, drawings and multimedia (audio/video) clips.
Enhanced metafile format (EMF) stores graphical images device-independently. Metafiles of EMF comprises of variable-length records in chronological order that can render the stored image after parsing on any output device. These variable-length records can be definitions of enclosed objects, commands for drawing, and graphics properties critical to render the image accurately.
You can also convert ONE into many other file formats. Please see the complete list below.