Headphones

Like your mother. Ok, this will be really really shallow but you'll get the idea. I'll throw in a bonus after.

💻 This is your music source (ipod, phone, pc etc..)

⚡ This is the signal (electricity that carries the music)

🎧 These are your headphones (signal goes to these)

So 💻 -----> ⚡ -----> 🎧

The signal carries the music from your ipod to your headphones but because of physics, there are factors that make it harder for the signal to reach the headphones easily. That's impedance. The resistance that makes it harder for ⚡ to get from 💻 to 🎧. If the impedance is higher then it's harder for the signal to get to your headphones, so you need something to help boost the signal like a more powerful amplifier.

So: High impedance headphones = you need a good amplifier to get the most out of your headphones

  Low impedance headphones = a basic should be 
  enough to drive your headphones well

Now the bonus: Sensitivity is another factor that tells you how much power you need for your headphones to be driven but think of it as the opposite

So if your headphones are highly sensitive then it can "hear" the signal better, even if the signal is weaker.

I tried not to use metaphors so I hope this helps. There's more to it, much more, but this will get you by till you're ready to take a deeper dive

Now go to bed. It's late ,😘