File Descriptions are a user-defined string that can be assigned to a file or folder, often used to keep notes about the file contents. Unfortunately Windows does not provide a standardised system for adding a user-defined description to files and folders. Opus does allow you to do this, and provides two different mechanisms for storing these descriptions:
Each of these two systems have their own advantages and disadvantages. The descript.ion system may be supported by other programs - for example, some image viewing tools support it, and you may want to enable this in Opus so that descriptions added by one program can be seen in the other. The disadvantages of descript.ion are that it is less efficient - every time a description is read or written, the descript.ion file has to be opened and parsed. The descript.ion files can also clutter up your file listings, although Opus does give you the ability to hide them if desired.
Using the NTFS comments system is more efficient than descript.ion and as alternate data streams are not normally visible, it can give a more elegant and unified feel to using file comments. The main disadvantage is that they are only supported on NTFS-formatted drives - if you're using another file system like FAT32, this system doesn't work.
You can choose which system you use from the File Operations / Metadata page in Preferences.
The options on the Copying Files / Metadata page let you control whether or not file descriptions are preserved when you copy files.
Whichever system you elect to use, you can assign a description to a file in two ways.
Use the Description command in the Properties drop-down on the default toolbar (or press Ctrl+P) to show the Set Description dialog.
The dialog displays the current description (if any) and lets you clear or edit it.
You can also set the description with the Metadata Pane or the Set Metadata dialog. These let you edit the description for selected files using the Comment field in the Extended Properties category.
See the Editing Metadata page for more information on using the metadata editor.