title: what is the roles of folder www, page, src in an ionic project?
body: <p>I am new in ionic. I found in some ionic project, there is no src(app &amp; pages) folder, but only is www folder. 
  After checking some sample ionic projects, it seems the src folder contents the similar components as www folder. </p>
  
  <p>Could you please explain the differences between these folders, are they can be used together? If there is some detailed introduction for ionic framework architecture, it will be really appreciated.  </p>