Earlier today I was in a UX design meeting and I used the terms "Secondary Tool" and "Primary Tool." (Application and tool are interchangeable terms.) Understanding the difference between these two is very important as their UX needs to be very different. Most application teams think that they are building a primary tool when, I am sorry to inform them, they are not. Very few teams work on primary tools. So what is the difference? I hope the following helps explain this.
A primary tool is one that the user uses daily. It is one where the user will have many sessions within a short period of time -- a few weeks. This rapid experience of having successes and recovering from failures builds the user's confidence in the his or her ability to use the tool. Moreover, this confidence encourages the user to explore the tool for better means to perform tasks and opportunities to use the tool for unforeseen outcomes. This confidence brings with it the need for far less feedback that an operation has been completed successfully and instead feedback can be limited to erroneous results.
A secondary tool is one that is not a primary tool. It is used infrequently -- less than once per week. This infrequency disposes the user to having to relearn the tool's operation at the start of a session. Only the most rudimentary operational knowledge is retained between sessions. The user is most successful when he or she is guided in performing a task from its beginning to its ending. Redundant orientation information such as task milestone displays, activity histories, and possible future work, etc are displayed beside the specific task step at hand. Feedback for success and for failure is always provided.