system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does fast charging work?

And how is it different from normal charging/ different fast charging? (qualcomm quick charge 2.0/3.0)
gpt
The limit on charging is down to how much power can be transferred into a phone. 

USB standard is 5 volts, at 0.5 amps. Multiply those together and it gives you 2.5 watts. 

Wall chargers tend to be higher amps, 1 amp, or even 2 amps, which would give you 5 or 10 watts. So two or four-times faster than charging with a computer. 

The problem is you can't keep increasing the amps, because eventually it would start warming the cable up and you'd get limitations like that. 

So 'fast chargers' became a thing. The phone has to be compatible, because what they do is abandon the 5V standard, and increase it to 9V at almost 1.7 amps. Multiply those together, and you get just over 15W, so it's six times faster than you'd get from charging with a computer.