So you finally decided to take the plunge and install Linux! Welcome to the club. Now the next step is to decide the flavour or distribution (distro for short) of Linux that you will install. So here's a guide to make the decision simpler for you.
What is a distro?
A Linux distribution (often abbreviated as distro) is an operating system made from a software collection, which is based upon the Linux kernel and, often, a package management system. Linux users usually obtain their operating system by downloading one of the Linux distributions, which are available for a wide variety of systems ranging from embedded devices (for example, OpenWrt) and personal computers (for example, Linux Mint) to powerful supercomputers (for example, Rocks Cluster Distribution).
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), a window manager, and a desktop environment. A desktop environment is separate from the distro and multiple can be installed simultaneously on a distro. Every distro comes with it's own set of pre-installed packages, and a package manager to install more packages. Lets move on to the various distro choices available.
Being one of the most ubiquitous distros, Ubuntu is also the best one to start with. It comes with Unity as the default desktop environment and APT as the package management system. You may also install Kubuntu, Xubuntu, or Lubuntu which come with the same Ubuntu distro but different desktop environments. KDE Plasma, which is the desktop environment in Kubuntu, is one of the most modern and popularly used ones.
Debian is the mother of Ubuntu and a good beginner distro. It is also a step up if you're familiar with Ubuntu and want to explore. The same familiar APT commands work but the default desktop environment is GNOME (which is among the best for touchscreen devices).
Linux Mint one of the most popular distros and strives to be a "modern, elegant and comfortable operating system which is both powerful and easy to use." It is based on Ubuntu and comes with Cinnamon as the default desktop environment. However, during the installation it provides you an option to choose the desktop environment of your choice. The same APT commands work hence it is a good alternative to Ubuntu as your first distro.
Elementary OS is also based on Ubuntu and uses the same update method. It comes with Pantheon desktop environment, which is similar to macOS in appearance, is also one of the best looking in the game. It is intended to be a "fast and open replacement for Windows and OS X."
openSUSE is a community-developed Linux distribution, sponsored by SUSE. It maintains a strict policy of ensuring all code in the standard installs will be from Free/Libre/Open-Source Software solutions, including Linux kernel Modules. SUSE's enterprise Linux products are all based on the codebase that comes out of the openSUSE project. There is also an accompanying rolling release version called openSUSE Tumbleweed, which is continuously updated with tested, stable packages.
Fedora is a popular distro that comes with GNOME desktop environment. Fedora has a reputation for focusing on innovation, integrating new technologies early on and working closely with upstream Linux communities. It is suitable for intermediate to advanced users. Linus Torvalds, the creator of the Linuxkernel, uses Fedora. Red Hat Enterprise Linux and CentOS are based on Fedora.
It is a lightweight distro and unlike Ubuntu, it comes with few preinstalled packages. It uses a rolling release model which means it has no version number and updates to packages are rolled out as they are made available upstream. It does not come with a desktop environment. The choice of which (and whether) to one install is left to the user. A big benefit of Arch Linux is the active user community and comprehensive documentation in the ArchWiki. It uses pacman package manager. Recommended for intermediate to advanced users.
Based on Arch Linux, Manjaro aims to take advantage of the power and the features that make Arch a great distribution while providing a more pleasant installation and operation experience out of the box both for new and experienced Linux users. It comes with KDE Plasma desktop environment and a software centre.
Slackware is the oldest Linux distribution under active development. It is a highly customizable distribution that stresses ease of maintenance and reliability over cutting-edge software and automated tools. Generally considered a distribution for advanced users, it is often suggested to those who want to learn the inner workings of a Linux operating system.
Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. In other words it is "The Distro of the hackers, for the hackers, by the hackers". Kali Linux includes many well known security tools, including nmap, aircrack-ng, wireshark, john the ripper and many more. Recommended for advanced users.