system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do touch screens work? 

I've always wondered how Iphones can differentiate between your fingers amd other objects such as stylus' and pencil erasers, etc. Does it have something to do with the heat from your fingers?
gpt
Remember that time when you went to Timmy's house and played on the trampoline? Bouncing around was fun! 

A touch screen works using a special kind of trampoline, called an electric field. At Timmy's house, when you stood on the trampoline, what did it do? It went down a little bit under your weight.

When your fingers touch a touch screen, they send out a teeny tiny bit of a pulse of electricity. This tiny bit of electricity pushes against the special electric field trampoline in the touch screen. So, just like you make a "bounce" in the trampoline by standing on it, the electric field on mommy's touch screen phone has a "bounce" in it from your finger!

The computer inside mommy's phone is very smart. It can tell where you touched the screen, where you put in the little bounce in the electric field, and it can use that information to help you do things like take a picture or throw those little birds at the piggies.

When you have more than one finger on the screen, it creates more than one bounce in the trampoline, and the phone computer is so smart, it can tell how many bounces you make with your fingers. It can even tell where a bounce starts and where a bounce stops.  That's why you can use two fingers and pull them away from each other to make the pictures on the phone bigger.