title: Difference between Variable and get_variable in TensorFlow
body: <p>As far as I know, <code>Variable</code> is the default operation for making a variable, and <code>get_variable</code> is mainly used for weight sharing.</p>
  
  <p>On the one hand, there are some people suggesting using <code>get_variable</code> instead of the primitive <code>Variable</code> operation whenever you need a variable. On the other hand, I merely see any use of <code>get_variable</code> in TensorFlow's official documents and demos.</p>
  
  <p>Thus I want to know some rules of thumb on how to correctly use these two mechanisms. Are there any "standard" principles?</p>