If you bought a new computer you would always have an 'installation disk', or if it did not exist you could create it through the operating system.
But since then things have changed and you can download any operating system online and easily create one bootable USB for any system you are interested in. Provided you have the right application to do it.
To create one bootable USB you need a disk image or ISO. ISO is basically a file that contains data that can be written to an optical disc such as a CD or DVD. It is essentially an installation disk.
For Windows 10, you can download the ISO image using Microsoft Installer. For all Linux distributions, you can download the ISO you are interested in from the official distribution page. You will only encounter problems if you try to find an ISO for operating macOS because they are not readily available. For specific ISOs you may need to search for torrents.
Let's create USB
Some operating systems, such as macOS, come with utilities for burning a disk image to a USB stick, but again, no. The MacOS utility is a bit complicated especially if you are a beginner.
Today we will try something simpler.
The tool Ethcher is available for Windows, Linux and macOS. All you need is an ISO file and a USB stick. The application will take care of everything else in three simple steps.
After its (easy) creation bootable USB, you can use it to start your computer from USB and not from your operating system. In some cases, you may need to change the boot order from your computer's BIOS to read USB first instead of your hard drive.