Conditional content is text and graphics that are included or excluded depending on a condition you specify.
A simple example is a reminder letter for an overdue account. The first and second reminders might have a subject line of “Reminder Notice”, but the third reminder letter might have the subject “Final Notice” and a different final paragraph.
A more complex example is a software manual for a product that comes in two versions, Pro and Lite. Both product versions have much in common, but the Pro version includes some features that are not in the Lite version. If you use conditional content, you can maintain one file containing information for both versions and print (or create online help) customized for each version. You do not have to maintain two sets of the information that is the same for both versions, so you will not forget to update both versions when something changes.