The Bank of England Base Rate (BBR) is set by the Bank of England (BOE) Monetary Policy Committee and is reviewed eight times a year. The rate is used to control money flow in the economy and can move up or down. It is likely that a tracker product rate will be linked to BBR. This means that the interest rate charged on your mortgage will increase or decrease in line with changes in BBR.
A discount rate is not usually linked to BBR but is likely to change if the lender decides to change their Standard Reversion Rate following a change in BBR. A fixed rate is not affected by changes in BBR during the fixed period.