Which app host model to use?

Hi,

  I am having the requirement that there are some web application which is running outside of sharepoint and it is running in different server. I want to use this application in Sharepoint 2013. It means that, when the user installed the app and once he clicked the app from the store and it should redirect to that application but it should be inside of Sharepoint 2013. I want sharepoint 2013 look and feel and inside sharepoint 2013 I want to display my application. Please suggest which type of app model should use and how to do it?

Balaji