What is Virtualbox ?
Oracle VM VirtualBox is a cross-platform virtualization application. It installs on your existing Intel or AMD-based computers, whether they are running Windows, Mac OS X, Linux, or Oracle Solaris operating systems (OSes). Secondly, it extends the capabilities of your existing computer so that it can run multiple OSes, inside multiple virtual machines, at the same time. As an example, you can run Windows and Linux on your Mac, run Windows Server 2016 on your Linux server, run Linux on your Windows PC, and so on, all alongside your existing applications. You can install and run as many virtual machines as you like. The only practical limits are disk space and memory.
How to install VirtualBox on Ubuntu ?
If you want to try on VirtualBox to install some other operating system like Mac OS X or Windows or even another version of Ubuntu on your existing ubuntu, open terminal and type command as,
$ sudo apt-get install virtualbox
To open just installed VirtualBox, type below command
Once, VirtualBox is opened you will see, VirtualBox icon is left sidebar on ubuntu, clicking on which you will see an Window like below,