Selections are a very powerful feature of the software and allow you to define criteria to create a sub-set of data to work with.
For example you may wish to have a selection that includes only options that are in the current season, and in a particular story.
You may create as many selections as you wish and choose to share them with other users. Note that the selection is just the definition of the criteria, the actual list of Products within it will vary as records are added, deleted and changed.