One of the new features in Excel 2010 and 2013, as discussed previously, are tools on the Ribbon that appear on demand, as you work. These tools will automatically appear as you work in your worksheet. They will be relevant to what you are doing at the time.
For example, if you are working with a PivotTable in your Excel worksheet, when you are working in your table, you will notice ANALYZE and DESIGN tabs, along with the PivotTable Tools, will appear on the Ribbon.
When you click away from the PivotTable, the on-demand tools will disappear, and the standard tabs will remain.