What does #[...] mean in emacs-lisp?

Question

I am puzzled by the expression

#[nil "\300\207"
      [nil]
      1]

as a value of skeleton-pair-filter-function.

Is this an alternative way of writing function in elisp? Or lisp in general?

Thanks.

Answer 1

It's a byte code function object, the result of byte compiling a function.

See manual entry here