title: tcl/tk button or toplevel pathname conventions
body: <p>When one creates a new toplevel or button in TK, one needs to enter a pathname.
  I have seen a basic code which looks like:</p>
  
  <pre><code>toplevel .a
  ...
  button .a.b ...
  </code></pre>
  
  <p>My question is:
  Are the dots treated differently than letters? Are they some sort of hierarchy delimiters, which create parent child relationship? I have looked at wiki TK and failed to find an answer to that.
  Many thanks,
  -Lior</p>