I am new to Ubuntu and I want to install VirtualBox in Ubuntu through terminal. Can you guys please provide me the command to install it?
Virtualbox is in the official repository.
Just open a terminal and enter:
sudo apt-get install virtualbox
After installing you should add the user, you want to use VirtualBox with to the vboxusers group by:
sudo adduser $USER vboxusers
If you prefer a more recent version, take a look at Download VirtualBox.
Help page from the Oracle VM virtualbox website. https://www.virtualbox.org/wiki/Linux_Downloads#Debian-basedLinuxdistributions
It has a list of deb packages you can download.
You can run it with
sudo dpkg Path/To/File