title: What does M1 mean in a maven repository?
body: <p>I've been using maven for a while, and I often review repositories before selected what version I want to use.  I don't entirely understand what the extensions mean.</p>
  
  <p>I know that when I see extensions like -RC1 and -RC2 that means release candidates.   When I see a version without an extension, I assume that means a released version.  But what does an extension of -M1 or -M2 mean?</p>
  
  <p>Example:</p>
  
  <p>2.8-RC1</p>
  
  <p>2.8</p>
  
  <p>2.8-M1  ??</p>