Difference between the two page_count variables?

[NCHASHIM]

What is the difference between $V{PAGE_COUNT} and ${MASTER_PAGE_COUNT}?    

I was using CONCATENATE("PAGE ",TEXT($V{PAGE_NUMBER},"#")," OF ",TEXT($V{PAGE_COUNT},"##") ) on my report, but I noticed in another question/answer that MASTER_PAGE_COUNT is preferred.  <Help> doesn't describe the difference.

[szaharia]

You can use $V{PAGE_NUMBER} and $V{PAGE_COUNT} in a report that contains no subreports and no report parts.
When used within a subreport, $V{PAGE_NUMBER} will display the current page number of the subreport itself, without taking into account other possible pages generated by the master report.
Also, $V{PAGE_COUNT} will display the total number of pages for that subreport.

The following variables can be used in subreports or report parts to display the current page number and the total number of pages for the entire document:

• $V{MASTER_CURRENT_PAGE} - for the current page
• $V{MASTER_TOTAL_PAGES} - for the total number of pages