title: Overlay image to make tutorial in Android app
body: <p>In many applications, I have seen that there is a welcome screen or tutorial that explains how the application works by overlaying explanations on top of the activity. For instance, in Android itself, the welcome screen with "Make yourself home".</p>
  
  <p>I would like to know what techniques can be used for that.</p>
  
  <p><em>Edit</em>: screenshot of "make yourself home
  <img src="https://i.stack.imgur.com/CSEXa.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/zL9rr.png" alt="enter image description here"></p>