title: What does "symbol" mean as in "Load Symbol List"?
body: <p>What does "symbol" mean as in "Load Symbol List"?  Or as in this example from MSDN:</p>
  
  <p>"#if lets you begin a conditional directive, testing a symbol or symbols to see if they evaluate to true."</p>
  
  <p>Where are these symbols defined and declared?</p>