I read the code when they added them. It may have changed, but here it is: 1) A hook adds a function or variable to one of several lists attached to the compon

I read the code when they added them. It may have changed, but here it is: 1) A hook adds a function or variable to one of several lists attached to the component object, when it's instantiated (yes, even your "functional" components are objects, and I don't just mean in the JS-functions-are-actually-objects sense—at least, they were when I read it) 2) Subsequent calls either call those functions, or accesses/modifies the value, in a FIFO manner, reading them out of those lists. This is why you can't mess with hook ordering in e.g. loops. It's basically just methods and properties on an object, but with FIFO access based on declaration order, instead of using a lookup table of some sort. [EDIT] A poster correctly pointed out (then deleted their post) that I wrote "loops" where I meant "conditionals". Technically sorta-true (though not quite, as phrased) if the loop isn't the same length every time, but yeah, I meant conditionals. Point is, the reason order matters is that the whole thing's just a bunch of FIFO queues, more or less.