I think it was the Linux kernel. There are many used with Linux now.
An application that runs in linux
ARMv8 on 2004
Linux
Security is a concept, not an application. You get security in Linux by making the system secure.
Linux is more powerful then windows
How the home laptop is used is the first thing to consider when choosing an operating system. Linux is free and comes with a suite of application software. Microsoft Windows costs are higher, and no application software is bundled with Windows. More games are available for Windows than for Linux.
On some Linux systems there is an application called "GNOME Do" which does that.
At a terminal prompt: sudo apt-get install <application-name>
Google Earth is its own application. It is launched directly.
Windows, mac os, Linux
You need to be more clear in what type of "interface" you are inquiring about. Linux has it's own API (Application Programming Interface) and ABI (Application Binary Interface). If you are referring to the user interface, Linux can have a GUI, a command line, or even no interface at all.
X Windows