Once search concepts and initial search terms are identified from the foreground question, they are plugged into the database with the goal of creating a working set.
A working set is the search string you've deemed the most appropriate for your question and its results. You will take these results to the next step of the Cycle: Appraise.
Identification of a working set is an iterative process. Often the initial search terms and how you combine them won't be your working set. You need to be aware of ways to adjust your results in order to arrive at the most appropriate search string.
Learn more with the Adjusting Results and Creating a Working Set tutorial.