DOCX was introduced with Microsoft Word 2007, it's based on open XML and uses ZIP compression for smaller file sizes. The benefit of having open XML is that it is able to be read by applications, platforms and Internet Platforms. However to open it using any Microsoft Word that predated 2007 would require DOCX to be converted into a normal doc format.
DOCX improves file and data management and data recovery. DOCX extends what is possible with the binary files of earlier versions. Any application that supports XML can access and work with data in the new file format. The application does not need to be a Microsoft product it can be any application. Users can also use standard transformations to extract or repurpose the data. In addition, security concerns are drastically reduced because the information is stored in XML, which is essentially plain text. Thus, the data can pass through corporate firewalls without hindrance.
Microsoft Word 2007 Microsoft Word 2008 (MAC) OxygenOffice Professional (Linux) Word 2010
The file type .mobi is an eBook format created by a French eBook company called Mobipocket which created a free software application for multiple devices including PDAs, smartphones and tablet devices. The company was bought by Amazon in 2005 and the support of the .mobi file extension was officially discontinued in 2011 with the AZW format superseding it.
Amazon Kindle Apple iBooks Mobipocket Reader Desktop