SA3 footprint size

Using Mac OS. I created a simple HtmlEditor app using SA2 and then created a SA3 web app using the Basic HTML Template. Publishing the SA2 app produces a folder containing file with a folder size of 45K. Publishing the SA3 app with a framework configuration build tools enabled and a build setting for Production this creates a folder containing file with a folder size of 6 M with the same framework configuration and build setting for Testing the folder size is 2.5 M. Most of the large size is because the resource folder contains an image folder. When I Publish the project with a framework configuration build tools disabled it creates the folder size is 57 K. With a build setting enabled a resource folder is created with a large size image folder, with build setting disabled resource folder is empty. My question is what, when and why use build setting enabled and as opposed to using build setting disabled? Is there any documentation to explain what enabling build setting in SA3 does and if there is please point me in the right direction thanks.