It is the fixed real interest rate that is paid on an inflation-adjusted notional. It is “real” in that, for each coupon, irrespective of the realized inflation in that same period, the actual interest paid (i.e., the nominal interest rate) is the same in “real” terms. So for example, if there is high inflation over the period of a coupon, the actual interest paid, i.e., the nominal interest rate, is higher; if there is low inflation over the period of the coupon, the actual interest paid is lower.
This is achieved by applying the fixed interest rate to the inflation-adjusted notional. For each coupon, the inflation-adjusted notional is based on the instrument's base notional, adjusted to take into account the change in the inflation index, a change that for each coupon is measured from the instrument's start date to that coupon's end date. Accordingly the actual notional for each coupon necessarily changes relative to the inflation index change in that period-if the inflation is high, the notional is higher; if the inflation is low, the notional is lower.
The real rate is only displayed for a Cross CCY Real Rate Swap and Real Rate Swap.
By default the system calculates this rate to the breakeven rate, i.e., the value that will result in a zero NPV.