Flexing budgets in context of variance analysis

What is the point in flexing the budget in the context of variance analysis? Does flexing imply that differences between the budget and actual volume of output are ignored in variance analysis? Explain your answer in the context of this weeks readings.
The for this week is required reading and can be found in the online library at the University of Liverpool:
Guven-Uslu, P. & Conrad, L. (2008) Uses of management accounting information for benchmarking in NHS trusts, Public Money & Management, 28 (4), pp. 239246, Wiley Interscience [Online]. DOI: 10.1111/j.1467-9302.2008.00650.x (Accessed 30 June 2009).
Textbook
Atrill, P. & McLaney, E. (2012) Management accounting for decision makers. 7th ed. Harlow, England : Pearson Education Ltd.
(Please note that the references to these readings can be found in the under the headings of the topics to which they relate.)
Budgets and strategic planning
Pages 187195 in Chapter 6 explore the role that budgets play within the strategic planning process. The authors also introduce the planning and control process.
Budgets for performance evaluation
Pages 196222 in Chapter 6 examine the intricacies of budgets, including the process through which they are developed. It is important to understand how budgets can be used to evaluate performance.
Variance analysis
Pages 2329254 in Chapter 7 discuss the process of analysing variations within budgets. The differences from original budget figures and actual figures must be examined in order to understand what changes occurred and what can be done to rectify the situationnamely, to reduce or eliminate the variation.
Effective budgetary control
Pages 254259 in Chapter 7 explore how organisations need to develop systems that support the budget process and how information is collected and reported. The authors also of management styles.
Standard costing
Pages 260268 in Chapter 7 examine how standards for costs, revenues, and quantities are developed by organisations when developing budgets. The reading also addresses considerations when using standards and problems that may occur.