title: BSON | terminal and non-terminal
body: <p>Reading through the <a href="http://bsonspec.org/#/specification" rel="noreferrer">BSON specification</a> I came across the <strong>terminal</strong> and <strong>non-terminal</strong> terms in it. For example:</p>
  
  <blockquote>
    <p>Valid BSON data is represented by the document <strong>non-terminal</strong>.</p>
  </blockquote>
  
  <p>&lt;...></p>
  
  <blockquote>
    <p>The following basic types are used as <strong>terminals</strong> in the rest of the grammar.</p>
  </blockquote>
  
  <p>What do “terminal” and “non-terminal” mean in the context of the BSON specification?</p>