Linux.
Ubuntu is a "distro" of the Linux operating system.
Yes, Ubuntu is an operating system, that uses the Linux Kernel.
Ubuntu - operating system - was created on 2004-10-20.
Ubuntu is free, it can not be pirated.
Linux is only a Kernel (Operating System). Different Flavours of linux have different user programs on top of the same linux kernel. A high level example : Ubuntu has the user program(package) GNOME while Kubuntu has KDE, whereas both ubuntu & Kubuntu use the same Linux Kernel.
You can use the Ubuntu operating system as you would use any other operating system! Unlike MS Windows, which is propriety and has to be paid for, Ubuntu is a free, open-source operating system that can be downloaded for free, and copied and given away as much as you like! I recommend searching Google for more info.
Windows 10 is currently a free operating system and can be downloaded on the Microsoft website, Ubuntu OS is also a free operating system, it can be Downloaded from the Ubuntu website Ubuntu.com/download
Ubuntu Server Edition is a free and open-source operating system for use in servers.
Ubuntu
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You have to install both operating systems to get a 'dual boot' system. I would suggest installing vista first, then installing ubuntu. Doing it the other way around will mean that the ubuntu installation will not be recognized after you install Vista, so do the Vista install first.The Ubuntu Grub loader will be able to recognize the Vista partition and should present you with a menu when you boot the machine as to which operating system you want to use.The easiest approach to this would be to install Vista on one partition and ubuntu on a different partition of your hard drive.
Ubuntu is an operating system, so just tell the installer to use the entire disk. However, an operating system is useless without software, and Ubuntu includes many software packages on a clean install.