With release of SharePoint 2013, Microsoft has been promoting isolated space idea for the code written for SharePoint 2013. Take example of workflows, which are now hosted in a different workflow service rather than within the SharePoint server.
Similarly, Microsoft has been promoting creation of apps for SharePoint rather than deploying Farm or Sandbox solutions. This model for apps works fine for most of the times. But at times this model of running the code out of SharePoint can be a pain in the neck. E.g. There are lots of files/content that needs to be deployed within the SharePoint site itself (remember, your SharePoint team site/mysite etc. becomes the host web for the app).
Earlier we used to create Modules to deploy files into SharePoint or if we wanted to deploy any content type etc. But that model is no more available within SharePoint apps.