I have been playing with C5 for about a week now. I am confused about 'built-in' page types and themes.

When I make a page type, I define editable areas. Then I go to defaults and add any blocks and stacks I want. Then I include it in composer.
When I go to composer and write a new page, I am presented with a form, based on my template for that page type. No issues

except:

So far, I have found 'blog_entry' and 'right_sidebar' have an additional field 'Short Description'. I find this odd, since there is no template in my theme for these page types. (yet, 'left_sidebar' acts like a template-less page type and uses default.php)

I have found these page types in the core concrete5 default theme. SO, it seems that C5 defaults to these. but adding page types here does not give them the same functionality as the ones that already exist.

If I create (or copy) these templates to my theme, and add a 'Short Description' area, I end up with two 'Short description' areas in composer.

I read frz's description of 'Short Description' here:
http://www.concrete5.org/community/forums/customizing_c5/what-is-th...

It explains the use but not the methodology.

1.Is there anyway to edit this field, without phpMyAdmin?
2.Are there additional fields or page types that are part of the 'core'?
3.Is there a list of page types that include the 'short description' field? (I would simply like to avoid them, if the field can't be accessed by page editor)
and finally,
4.What is the purpose of having two meta description fields?
(meta description and keywords are both already available to composer. why force a second entry field?)

Thanks for any insight.
-Dylan