Let's put the last 25 years of Linux in perspective with these 25 stunning facts about Linux.

Fact #1: There are 115 million lines of code in The Linux Foundation’s collaborative projects. Compare this to the 45 million lines of code in Windows XP.

Fact #2: The Linux kernel is by far the most active open source project on Earth. Its accepts an average of 185 patches each day.

Fact #3: It’s taken about 41,000 person-years to build Linux — the equivalent of about $5 billion in developer salary.

Fact #4: The Linux Foundation pays Linus $10 million per year to continue his work on Linux. His net worth is $150 million.

Fact #5: Despite this the sums of money involved — and all the systems that rely on Linux — Linus works from home, alone, with his cat.

Fact #6: While Linus was serving as in the Finnish military — doing ballistics calculations — he bought a copy of Andrew Tanenbaum’s Operating Systems: Design and Implementation. This book described Minix — a simplified educational version of Unix — and opened Linus’s eyes to the Unix philosophy.

Fact #7: Even though Torvalds wrote 100% of Linux’s first release, his original contributions now account for less than 1% of its total codebase. These days he says he’s too busy merging in code written by other contributors to do much programming himself.

Fact #8: Other famous software icons like Bill Gates and Mark Zuckerberg dropped out of college to pursue their projects full-time. Linus not only continued school after the initial success of Linux — he even stuck around to get his masters in computer science.

Fact #9: Even though Linus created Git, he doesn’t accept pull requests through GitHub. Linux is listed on GitHub, though, and it has more than 35,000 stars.

Fact #10: Linux’s mascot is a penguin named “Tux”:

Fact #11: Developers from a wide range of companies contribute to Linux.

Fact #12: 97% of the world’s supercomputers run on Linux — including clusters used by NASA.

Fact #13: SpaceX uses a special fault-tolerant design of Linux in each of its Merlin rocket engines. Through this, Linux has helped complete 32 space missions.

Fact #14: In 2009, the government of Munich, Germany switched from Windows to Linux. They claim to have saved more than €10 million in software licensing fees so far. But the switch may have cost them that much or more in lost productivity.

Fact #15: Linux powers the tiny $5 Raspberry Pi computer.

Fact #16: Is Linux the king of the world? Titanic was the first feature film produced on Linux servers.

Fact #17: Even though video game developer Valve’s founder Gabe Newell has publicly stated that he thinks Linux is the future of gaming, his company’s Linux-based Steam Machine console flopped. Linux’s overall market share has fallen a bit since 2010.

Fact #18: Dronecode is Linux for Drones. About 1,000 companies develop drone services that run on top of this operating system.

Fact #19: Toyota and Jaguar plan to run their future cars using Automotive-grade Linux.

Fact #20: Linux is available in many distributions, or “distros.” Most distros are based off of other distros. The most popular distro is Ubuntu, which is based off of Debian.

Fact #21: Red Hat is a company that makes an enterprise-focused distribution of Linux. It is the largest company built around open source software, and is on track to make $5 billion in revenue this year.

Fact #22: Linux doesn’t necessarily come with a graphic user interface (GUI). Many developers interact with it through a command line shell — usually Bash. You can choose from a variety of GUI shells, such as Xfce and KDE. When you hear the term “Xubuntu”, it means “Ubuntu with Xfce.” Can you guess what “Kubuntu” means?
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Fact #23: Linux uses the GNU General Public License.
“The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software — to make sure the software is free for all its users.” 

Fact #24: Linux uses a “Unix-like” design, where it's monolithic Linux kernel oversees file systems, networking, and process control. The rest of the functionality is handled by modules — many of which are from the GNU project.

Fact #25: Even Microsoft Windows — Linux’s biggest competing operating system — is embracing Linux. It recently integrated Ubuntu Bash into Windows 10

Source: https://medium.freecodecamp.com/linux-is-25-yay-lets-celebrate-with-25-rad-facts-about-linux-c8d8ac30076d#.gqcqbodo0

You can add any other fact you know about Linux if you think it not listed here.