Confused about default.php vs home.php

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I'm still new to CC5 and I thought I had things straight when I copied my downloaded the free theme "Flexcrete" to root/themes to customize it. I had previously installed two other free themes to try out but had never moved them to root/themes because they did not seem to fit my webpage as well.

Two weeks later I now discover that I have been making changes to the default.php not the home.php. When I look at pagetypes I see three different "home" pagetypes.

name handle package
Home home Foundation
Homepage homepage Rigid Light theme
homepg homepg None

I thought Flexcrete showed up as the package for homepg before I moved it to root/themes but now I don't see any home pagetype assigned to my customized Flexcrete theme. I tried to add a new pagetype and assign the name "home" and handle "home" but it said it was already in use - and of course it is - for Foundation. How do I get my theme to use my home.php and not the default.php?