This is the key to custom reporting. A user may change how the data is presented in any of the supported ways (filtering, grouping, sorting etc) and the result can be saved as a named layout. This simplifies the process of getting back to the same point in the future and allows a My Flexquery entry to launch straight back into the same configuration. Fields shown or hidden are stored, as well as their column position. Group subtotals and grand totals (also user-defined) are retained and stored in a saved layout.
As pivots open up enormous potential in terms of creating your own summary totals, saved layouts allow many different views of your data to be saved for easy retrieval later.