The Node.js ecosystem is huge and thanks to it V8 also powers desktop apps, with projects like Electron.
and many others exist as well.
V8 is written in C++, and it's continuously improved. It is portable and runs on Mac, Windows, Linux and several other systems.
In this V8 introduction, we will ignore the implementation details of V8: they can be found on more authoritative sites (e.g. the V8 official site), and they change over time, often radically.
On the web, there is a race for performance that's been going on for years, and we (as users and developers) benefit a lot from this competition because we get faster and more optimized machines year after year.
Our applications now can run for hours inside a browser, rather than being just a few form validation rules or simple scripts.