Gears

You don't need to be in a certain gear to deal with a certain feature on the road. Your CONTEXT defines your safe SPEED, which in turn defines the best GEAR.

An automatic car changes gear for you, depending on how much power is needed from the engine to move. Electric cars don’t have gears: they simply move by magnetic repulsion.

In a manual car, you'll need to use the clutch before you change gear. That disconnects the engine from pushing the wheels around. (Think how a short-legged runner would need to disconnect their feet from the ground first, before they could "change to longer legs" to stride ahead faster).  See what happens when moving the "gearstick".

Gears allow faster travel without the engine overheating.  They are simply levers arranged around wheels of different sizes, kept in a box.  So, the same push from the engine can move the car a small distance quickly OR it can move a big distance slowly.  (Think how short-legged people take less effort to walk up a hill than long-legged ones).

​A gear-change should be made at  (1)  the right speed,  (2)  when your left hand is free,  (3)  if there's no activity outside, and  (4)  at a good pace.