If you are a beginner, the first question you get into your mind when you are learning Linux.
What is Linux?
If you google it, you will get it is an operating system and etc.
To know for what and why Linux is used, we need to go back to history. In the early '80s, Richard Stallman working in a lab at MIT started a GNU project to create an open-source operating system. This all started because of a new printer in the lab. But the license is restricted him to modify the code. He hacked the earlier printers to electronically send the messages to the user who printed items when printing was completed. As well as to notify other users that the printer is free to use.
By the early '90s, there was sufficient GNU software to create an entire operating system. However, the kernel which is the heart of the GNU was not still complete. Meanwhile, in the early '90s, Linus Torvalds set on a hobby project to develop UNIX like kernel known as Linux and used GNU software such as GNU's C compiler to do it. At the same time, Kernel on its own was useless. He ended up including GNU software with a kernel to release an operating system. Later, Richard Stallman's free software foundation sponsored the group Debian to release a GNU-Linux distribution that was entirely open for people to use and contribute too.
Debian, over the years, grew from a small group of free software foundation for Hackers to an enormous community today due to its popularity. Debian became the base of countless Linux distribution as it is an open the software which allows everyone to read the source code, modify it, and redistribute as well. So there are may distro available now.
When there are numerous Linux distributions available, the beginner is confused to choose which one?
Answe: Ubuntu
Ubuntu is the most popular and suggested distro for beginners. Ubuntu was started in the early 2000s, and it is owned by "CANONICAL". Ubuntu is now very popular which is used as a base for a new operating system. Ubuntu has been derived from Debian which includes desktop environment called Unity. The recent advancement has mobiles which run on the new version of Ubuntu. Canonical aims to fixes bugs and does upstream ( that they send changes back to Debian to include in the future release).
While Debian releases a new version periodically, Ubuntu's aim is to capture the stability of Debian. This ensure that for every release the new version of Debian Canonical release two distribution in a year, one in April and the other in October. The naming convention of Ubuntu is the year and month. So the version will be released in October 2020, and it is called Ubuntu 20.10. Every 2 years in April, a long term support version is released called LTS, which is officially supported for the 5 years. Releases in between LTS version are only supported for 9 months.