What's the difference between tf.placeholder and tf.Variable?
<p>I'm a newbie to TensorFlow. I'm confused about the difference between <code>tf.placeholder</code> and <code>tf.Variable</code>. In my view, <code>tf.placeholder</code> is used for input data, and <code>tf.Variable</code> is used to store the state of data. This is all what I know. </p>

<p>Could someone explain to me more in detail about their differences? In particular, when to use <code>tf.Variable</code> and when to use <code>tf.placeholder</code>? </p>