The price matrix is used for
overriding normal prices for rentals. You can make a special
price for any item type (new, reg, etc.) for any or all days
of the week, a certain date, and a particular time of day.
It will also let you override the days to rent, or let you
choose the days to rent at rental time, and it will
automatically bring in the appropriate price.
You can also
create a price matrix for certain members only, so perhaps
your employees get to rent at a discounted price.