Using the "Extended Help" section on the bottom of the field descriptor, you can provide extended help text and HTML to your users.
If a user is making changes to data or simply trying to understand a data field, a WOW developer can provide a description of the fields as follows.
Clicking on the key will lead you to the field descriptor manager for the Employee# column. Scroll down to the extended help section, and insert what you want the help box to describe.
When a field is displayed on the UI and question mark image will appear next to it allowing the user to click on the icon and display the helpful text to the user.
If you click on the field help button, the help window will open providing any descriptive details about the field.
It is not necessary for the field to be a key field, any of the fd managers will allow field level help.