title: What is greenlet?
body: <p>I am new to gevent.I have read introduction from <a href="http://www.gevent.org/intro.html#example" rel="noreferrer">gevent</a></p>
  
  <p>They have provided simple examples but I am struggling to understand what greenlet is.From Learning Concurrency.</p>
  
  <pre><code>Greenlets are a very lightweight coroutine written in C that
  are cooperatively scheduled. They provide us with a very lightweight thread-
  like object that allows us to achieve concurrent execution within our Python
  programs without incurring the cost of spinning up multiple threads.
  </code></pre>
  
  <p>Greenlets are not threads?
  How is synhronisation point defined? Could somone explain with examples?</p>