title: TFLearn - What is input_data
body: <p>I came across the following statement:</p>
  
  <pre><code>convnet = input_data(shape=[None,img_size,img_size,1], name='input')
  </code></pre>
  
  <p>I tried looking for a description, but couldn't find a clear explanation.</p>
  
  <p>My main question here is what is the function <code>input_data</code> mainly doing? Is it like a place holder for our input data?</p>
  
  <p>Regarding the shape, what is <code>None</code> at the beginning, and <code>1</code> at the end?</p>
  
  <p>Thanks.</p>