Virtualbox works very good if you add one or more virtual machines like Ubuntu, Centos, Mint, Puppy, Kali and Windows. Normally, a new virtual machine can connect to the Internet and be run in its own world. However, the time could come when you want to go back and for between you pc and the virtual machine, and, this includes copying and pasting files from one operating system to the other. Well, here is where 'Guest Additions' comes into play. 'Guest Additions' is included with Virtual box. Alternatively, you can download and install it with the Linux command line.Once you have 'Guest Additions' working, you can change the appearance of the screen and copy and paste text from your pc to the virtual machine. The 'host' key on your computer is the [right ctrl] key.
The commands below show how to change the appearance of your Virtualbox. Host F and Host L give nice, large screens. The default screen may be host C which may not be that desirable.
To copy and paste from pc to virtual machine,
1) Select Devices >Drag and Drop >Host To Guest
2) Select Devices >Shared Clipboard >Host To Guest