Fixed rate loans have the interest rate fixed for a specified period. This protects you from interest rate rises for the period you have fixed the interest rate. Fixed rate loans give you financial certainty each month during the fixed interest rate period. You know exactly what is your weekly or monthly mortgage repayment is. At the expiration of the fixed interest rate period, you could choose to have another fixed interest period or revert to a variable interest rate loan.
The disadvantage of fixing the interest rate is that if the interest rate is reduced by the lender, you would continue to pay the higher interest rate for the selected period.