A DB pension scheme is classed as one of the best pension schemes on the marketplace because they guarantee a set income for life. They are now quite rare due to the complexity of running them.
In the past, you likely would have paid a fixed percentage of your income (usually 5-15% of your salary), alongside an employer contribution (that may vary from year to year). Being part of this scheme meant you’d get a pension for life. Your entitlement value is based on your number of years in employment and your final salary before leaving.
Even if your retirement age is a long way from the future, your entitlement must stay in line with inflation. So even if the market changes, they must still make good on your pension. This is different from taking on the risk yourself.