It is mostly intended for teaching basics of programming. Used in lots of schools all around the world. Gets around 500 daily users.
There is a series of interactive tutorials: https://flowrun.io/tutorials
Also a free ebook: https://leanpub.com/learnprogrammingwithflowrun
Editor is open source: https://github.com/sacode387/FlowRun
Supports debugging, custom functions and recursion even.
This is an alternative to Flowgorithm, which only works on Windows.