How do hybrid cars use less fuel? Isn’t efficiency wasted in the extra conversions of energy?

Alex C questioned:

I’m thought of hybrids that have a gas motor and gripping. If they aren’t exciting with electricity externally, all of the energy to run it comes from gasoline. Therefore, how is it more fuel efficeint to conveying energy via an elctric motor to a battery and then back to the wheels via the motor again to use for handbook (at slow speeds or when they do this)?

So how do the hybrid cars work?

Brian questioned:

What do they use the gripping motor below 30 and the gas motor only on the highway or both?