(Graphical User Interface - much like Windows) or as a dual-boot system. A dual-boot allows you the choice of starting the computer with Windows or Linux.
The Linux side includes but not limited to:
- a suite of Office tools compatible with, but more friendly than Microsoft Office.
- although not a necessity, a anti-virus program
- audio/video players
- graphic viewer/editor with more features than Microsoft tools.
- access to thousands of other programs that are compatible, and more often than not, better than Microsoft's array of tools. 
- a secure easy-to-use privacy-enhanced browser with access to the Internet and what is being flogged as the "Deep web". This also provides access to the the "Dark Net", and any access to the DW is your decision and use is your responsibility.