Ubuntu is a Linux distribution (as in a specific OS setup with the Linux kernel.)
It would depend on what the user/business is going to be using the machine for. For example, using a Linux machine for the sole purpose of playing AAA titles is not th best idea at the moment. You could use a Linux/Microsoft Office combo if you know how to get it working.
Switch to Linux.
Android is a Linux based operating system means you are already running Linux over your smart device ! And you can switch Android with some other Linux version !
The use of a Linux Virtual Machine is to run a copy of Linux on your current operation system. This will allow you to run various applications that only run on Linux.
Kernel, but I guess when you will learn, you will have to switch (Ubuntu for programmers and gamers and Kali Linux for penetration testers and hackers)
It allows you to switch users.
To log into the system.
The purpose of a man page is to display instructions for the usage of a program.
Linux does not have a target market. It is designed to be easily adapted to whatever purpose a person or company needs.
su = switch user RTFM, Luke...
Reboot or switch to Linux.