Why do I have to omit parentheses when passing a function as an argument?

Question

I am trying to wrap my head around as to why the following code results in a stack overflow when the parentheses are included, but do not when they omitted.

I am ca

Answer 1

By writing

foo()

you're actually calling foo at that moment. Which of course then calls foo() again...until you stackoverflow.

In case 2 you're effectively passing a "reference" to foo, saying "run this in 2s". Not actually calling foo().

So use parens when you actually want to invoke it. Not when you want to refer to it.