Basically, WhatsApp Tri-Crypt aims to help you recover WhatsApp conversations that were deleted from the device, with the goal (presumably) of finding out who a person had conversations with, or what about. Basically, it's an app for spying.
WhatsApp Tri-Crypt has many uses, although the most common (and least ethical) is the one mentioned above. Whatever reason you want use this app, you may want to consider what you would think if someone else used the app for the same reason. Fortunately, the free version doesn't let you deactivate its notifications.