title: What is a regular language?
body: <p>I'm trying to understand the concept of languages levels (regular, context free, context sensitive, etc.).</p>
  
  <p>I can look this up easily, but all explanations I find are a load of symbols and talk about <em>sets</em>. I have two questions:</p>
  
  <ol>
  <li><p>Can you describe in words what a regular language is, and how the languages differ?</p></li>
  <li><p>Where do people learn to understand this stuff? As I understand it, it is formal mathematics? I had a couple of courses at uni which used it and barely anyone understood it as the tutors just assumed we knew it. Where can I learn it and why are people "expected" to know it in so many sources?  It's like there's a gap in education.</p></li>
  </ol>
  
  <p>Here's an <a href="http://www.cs.odu.edu/~toida/nerzic/390teched/regular/reg-lang/definitions.html" rel="noreferrer">example</a>:</p>
  
  <blockquote>
    <p>Any language belonging to this set is a regular language over the alphabet.</p>
  </blockquote>
  
  <p>How can a language be "over" anything?</p>