running total is line by line total 
Ex : Debit credit Balance

the balance is the running total

sub total is after last record 
exp : Debit Credit
Balance 
The balance us sub total

running total gives total of value at the end of Page.
 if you have 5 pages of data. Each page contain 10 row of 
data with each column's value as 1. Then running total will 
give you value as 10 on1st page 20 on 2nd page 50 on last 
page. 
Where as Sub Total will give you value 50 only.

A subtotal is a summary that totals or sums numeric values 
in a group.

Running totals are a flexible and powerful way to create 
specialized summaries and continually incrementing totals.