You can go read the Wikipedia article if you want to understand “that” part… I guess, idk, go fuck yourself!!!

Some YouTube math video about lambda calculus, the asshole casually said “you can check the Wikipedia article” on an aspect that didn’t fit inside his 10-minute video. As if Wikipedia didn’t frustrate even professional mathematicians themselves, with the obtuse exposition and a thousand notations and citations.

Fortunately, there are other math educators on YouTube.
On the topic of lambda calculus, search for this title:
PLUS times PLUS

It’s wild stuff! It’s as if like math is like a shirt, and lambda calculus pulls one arm inside out, there are some weird logical seams in math when you use different tools with the same numbers.