title: When I push a image to Docker Hub... does the image is a "snapshot" of all customizations.. or is created again when you pull/run it?
body: <p>Learning Docker here... I have a simple question. I can't figure out the following.</p>
  
  <p><strong>Today, Alice build and push her custom image</strong> to Docker Hub:</p>
  
  <pre><code>FROM alpine
  
  RUN apk add --update --no-cache mysoftware
  </code></pre>
  
  <p>When Alice build the image, <code>mysoftware</code> (say version <code>1.0</code>) will be added to the image.</p>
  
  <p><strong>Next week, Bob pull the image</strong>. In the meanwhile, <code>mysoftware</code> has bumped to <code>1.1</code> version. Does bob gets the updated version of <code>mysoftware</code>... or the <code>apk add mysoftware</code> command is "freezed" at the time that Alice build/push the image?</p>