Microsoft says it will be slimmer and trimmer than its desktop predecessors. Power-saving capabilities will be enhanced to save battery life on mobile devices, and certain functions will be cut out to save disk space on the typically smaller SSD drives in tablets.
Some of the functions that will be cut out in the new release, according to the article are:
“macros, add-ins, and features that rely on ActiveX controls or third-party code, as well as legacy features such as the ability to play older media formats in PowerPoint and edit equations written in Equation Editor 3.0, used in older versions of Office.”