1. Linux History and Distro

1.1 History

Dennis Richie and Ken Thompson developed C language and Unix os at AT&T Bell Labs in 1969 and the source code was shared with the world. In 1975, Unix was sold but half of the source code was written by others(hippies in Berkeley California).

This resulted in 2 versions of Unix:

AT&T Unix - the official one
BSD Unix - free one

(BSD had many descendants like FreeBSD, OpenBSD, NetBSD< DragonFly BSD and PC-BSD)

By the 1980s, every company started to design their own Unix system which lead to a mess(basically there were so many different ways to do the same task). So, this lea to the root of Linux. Richard Stallman aimed to end this era of Unix separation and everybody re-inventing the wheel by starting the GNU project. Most of the command line tools you use today are GNU tools.

In the 1990s, people embraced the combination of this kernel with the GNU tools written by Linus Torvalds(he bought a 386 computer and wrote a brand new POSIX-compliant kernel).

2015 was the Linux revolution. Most used os.

1.2 Linux Distros

1.2.1 What are Linux Distros?

A Linux distribution is a collection of (usually open-source) software on top of a Linux kernel.

A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System, or, more recently, Wayland), a window manager, and a desktop environment.

Most of the included software is free and open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software.

1.2.2 Various Distros

Red HAt, Ubuntu, Debian, Linux Mint, Fedora

That's all, thanks for reading :)

References:

Linux Fundamentals- Paul Cobbaut

Wiki