title: Please explain some Javascript Regular Expressions
body: <p>I'm learning Javascript via an online tutorial, but nowhere on that website or any other I googled for was the jumble of symbols explained that makes up a regular expression.</p>
  
  <p><strong>Check if all numbers:</strong>  /^[0-9]+$/</p>
  
  <p><strong>Check if all letters:</strong> /^[a-zA-Z]+$/</p>
  
  <p>And the hardest one:</p>
  
  <p><strong>Validate Email:</strong> /^[\w-.+]+\@[a-zA-Z0-9.-]+.[a-zA-z0-9]{2,4}$/</p>
  
  <p>What do all the slashes and dollar signs and brackets mean? Please explain.</p>
  
  <p>(By the way, what languages are required to create a flexible website? I know a bit of Javascript and wanna learn jQuery and PHP. Anything else needed?)</p>
  
  <p>Thanks.</p>