We are all familiar with Microsoft Word, Excel and Powerpoint.
But in case you do not know, personal computing trend is now being more on internet-based and mostly used via a tablet.
Those are areas that original MS Office is designed to be used for, since MS Office is basically, at its core, to be used in a PC.

Thus, most user are starting to use Google Docs and other web-based services to store documents and stuffs.
In response to this scenario, Microsoft tried to augment its launch of tablet by providing softwares that will actually support it and makes it easier to use.
This new version of Microsoft Office is more of usage for the Windows 8 OS. An OS geared toward tablet computing, and basically one of the pieces of puzzle that Microsoft needs to do in able to cope up with the ever changing trend of technology.