title: What are Free and Bound variables?
body: <p>I've been programming for a long time (too long, actually), but I'm really struggling to get a handle on the terms "Free Variables" and "Bound Variables".</p>
  
  <p>Most of the "explanations" I've found online start by talking about topics like Lambda calculus and Formal logic, or Axiomatic Semantics. which makes me want to <a href="http://en.wikipedia.org/wiki/That%27s_When_I_Reach_for_My_Revolver" rel="noreferrer">reach for my revolver</a>.  </p>
  
  <p>Can someone explain these two terms, ideally from an implementation perspective. Can they exist in compiled languages, and what low-level code do they translate to?</p>