Again, if we say "let function" that is not accurate. let is an operator that creates a new nesting of the lexical scope in which it binds some variables, and then evaluates forms in that environment.

let implements something similar to what is achieved with a combination of special syntax in some other languages.

    Lisp                                 C

    (let ((x 1)                          { int x = 1;
          (y 2)                            int y = 2;
      (foo x y))                           foo(x, y); }

Both of these mean "create fresh instances of variables x and y, which are scoped only to this construct, initializing them with 1 and 2, and then call foo with x and y arguments."

The syntax of LET is

   let ({var | (var [init-form])}*)
     declaration*
     form*