title: Meaning of different taglib-standard*.jar
body: <p>When I land on the download page of <a href="http://tomcat.apache.org/download-taglibs.cgi" rel="nofollow noreferrer">Apache Taglibs</a>, I can see 4 types of JARs, namely:</p>
  
  <ol>
  <li>impl</li>
  <li>spec</li>
  <li>jstlel</li>
  <li>compat</li>
  </ol>
  
  <p>What is the difference between each of these variants?</p>