Consider I want to make a new theme for my workbook. First (for the colors) I go through Page Layout > Themes group > Colors > New custom colors.
In this dialog box There are 4 text/backgrounds, 6 Accents and two hyperlinks.
My problem is how exactly they work?

On the right-hand there are two samples with texts and charts when I click those text/backgrounds orAccents these two change, but I can't figure out completely how those buttons affect real final theme.
Or, simpler, what are the meanings of those text/backgrounds or Accents buttons?