New Microsoft Office 2013 features you need to know about
Logging into Microsoft Office 2013 allows Office to be connected to Microsoft OneDrive. OneDrive is Microsoft's cloud storage system for consumers. Not only does Office 2013 support OneDrive, but OneDrive is the default location for saving Office documents.
It is also part of Microsoft's renewed focus on file sharing and social collaboration. Note that Microsoft recently increased the storage limit for Office 365 users.