Repo Rate refers to the repurchase rate. This is the rate of interest at which the commercial banks borrow money from the Central bank against securities with the promise to buy them back after a certain time period. Similarly the Reverse Repo Rate is the rate at which commercial banks lend to the Central bank. Reverse Repo Rate is always lower than the Repo rate by few basis points.
When the repo rate is reduced, the loan becomes cheaper for the commercial banks, which also reduces interest rates on loans for general customer. The fall in the rates of interest increases the demand for loans for investment and consumption purpose. Hence, aggregate demand has started rising. Similarly, when the Reverse beneficial for banks than the repo rate, it is not Central Bank and they like to extend funds with the general public with that fund, thus, loans to the the credit. This also has a positive impanding aggregate demand in reducing the deflationary gap.