About the library used behind: Driver.JS
Powerful, highly customizable vanilla JavaScript engine to drive the user's focus across the page.
No external dependencies, supports all major browsers and highly customizable.
Simple: is simple to use and has no external dependency at all
Highly customizable: has a powerful API and can be used however you want
Highlight anything: highlight any (literally any) element on page
Feature introductions: create powerful feature introductions for your web applications
Focus shifters: add focus shifters for users
User friendly: Everything is controllable by keyboard
Consistent behavior: usable across all browsers (including in-famous IE)
MIT Licensed: free for personal and commercial use
So, yet another tour library?
No, it is not. Tours are just one of the many use-cases. Driver.js can be used wherever you need some sort of overlay for the page; some common use cases could be: e.g. dimming the background when user is interacting with some component i.e. the way Facebook does when you try to create a post, using it as a focus shifter to bring user's attention to some component on page, or using it to simulate those "Turn off the Lights" widgets that you might have seen on video players online, etc.
Reference: https://kamranahmed.info/driver.js/