A discounted mortgage offer a reduction off the standard variable rate for a set period usually shown as a fixed percentage reduction to the lender's normal variable rate e.g. 2.00% below variable rate for 2 years.

If interest rates fall further, the rate that you will pay will also go down. 

However, when interest rates rise, so will your mortgage payments. 

A discount rate mortgage can be attractive for people who are on a tight income when they first take out the mortgage, but are confident their income will increase in the future.