Glossary
Downshift means that you shift down from, for example, 3rd gear to 2nd gear. You use downshifting when you reduce speed, regardless of whether you brake yourself or if you are driving uphill, for example.
You then start by braking to the new speed and then shift down. If it is a case of a sharp reduction in speed, you can also skip gears, for example from 4th gear to 2nd.