The actual wikipedia page has a bunch of links that the OP doesn't include. To me, this is the opposite of code golf; rather than trying to concisely express the concept in the language's "builtins", it instead delegates the underlying concepts to their own "functions", and only describes the relationship between these concepts.

https://en.wikipedia.org/wiki/Concatenative_programming_lang...

If you know what the linked terms mean, you can move on quickly. If you don't, then explaining the higher-level concept in a way that skips these building blocks would be a waste of time; it's a better use of everyone's time for readers to at least skim the linked articles, first.