What are the advantages and disadvantages of using high gears versus low gears on a bike?

Using high gears on a bike can make pedaling easier and faster, which is advantageous for riding on flat terrain or going downhill. However, it can be harder to pedal uphill or start from a stop. On the other hand, low gears make it easier to pedal uphill or start from a stop, but can make it harder to pedal at high speeds or on flat terrain.