system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 How does paracetamol work?
gpt
We don’t know exactly yet. 

Regarding other painkillers like Ibuprofen/Naproxene/Asprine/Metamizol (so called NSAID/NSAR), they all influence one of your bodies enzymes (as you requested an Eli5: A tiny chemical tool that will produce or modify something), called cyclooxigenase (COX). This enzyme produces substances that will cause fever, pain etc. because these symptoms are a warning sign to your body that something is wrong. 

A really basic explanation lacking many things: NSARs will reduce the activity of COX and therefore will inhibit the production of substances that cause fever, pain etc..

Paracetamol however, is different. There are multiple theories, but the one that’s taught in medical school mostly is, that paracetamol modifies the way your brain will perceive pain. 

eli5: Your brain will think about pain as less terrible and less alarming when it’s under the influence of paracetamol, either because the pain information is received less & later and/or the understand of „pain“ is changed. 

Btw: Changing the perception of pain is the major effect of all opioids. They are several magnitudes more efficient then paracetamol but also far more dangerous.