Comment by FrozenVoid

The idea is that all LISP code is data that is easily altered, essentially https://en.wikipedia.org/wiki/Abstract_syntax_tree encapsulated in parens.

LISP syntax is uniform,everything(functions,data,argument lists) is nested lists of lists like (list(list(list))), so that allows altering specific places "in-the-list"(place 1,2,3...) as form of meta-programming,

where normal syntax FOR( A IN B) would be written roughly as (for a b) where for is used as a function taking 'a' and 'b' as parameters, but in this form(where 'for' is just the first element of the list) you can have functions that "alter-the-list" by example (replace-first-list-element (for a b) replacement-part) returns (replacement-part a b).