linux: added general linux entry

wiki/games/lutris.md

@@ -1,7 +1,7 @@
 # Lutris
 
 [Lutris](https://lutris.net/) is a free and open source video game platform for
-Linux systems.
+[Linux](/wiki/linux/linux.md) systems.
 It features compatibility with [GOG](https://www.gog.com/),
 [Humble Bundle](https://humblebundle.com/),
 [Epic Games](https://www.epicgames.com/), [Steam](/wiki/games/steam.md) and many

wiki/linux/arch-linux/arch-linux.md

@@ -1,6 +1,7 @@
 # Arch Linux
 
-[Arch Linux](https://archlinux.org/) is a rolling-release, general-purpose Linux
+[Arch Linux](https://archlinux.org/) is a rolling-release, general-purpose
+[Linux](/wiki/linux/linux.md)
 distribution.
 Arch Linux uses the [pacman](./package_manager.md) package manager.
 The Arch User Repositories (AUR) features community-made packages that can be

wiki/linux/linux.md

@@ -0,0 +1,14 @@
+# Linux
+
+Linux is a family of open-source operating systems that are based on the kernel
+with the same name.
+Linux based operating systems are Unix-like.
+
+## Distributions
+
+The different operating systems that are based on the Linux kernel are called
+distributions.
+
+- [Arch Linux](/wiki/linux/arch-linux/arch-linux.md) is a rolling-release
+  distribution whose base system is as minimal and needs heavy user
+  configuration.