system
A chat on subreddit /r/pcmasterrace
human
I immediately knew what it was, glad you figured it out. No idea why most cases don't come with them anymore. Better than going into windows and having the power button do different things when holding while powered on.
gpt
It is not a restart Button. It is a reset Button.
Your Windows restart button will safely shutdown all processes and services that are running. It will also male sure alle data is written to disk before shutdown / restart.

The reset button Interrupts the cpu and kills all running processes. It should only be used if your os is stuck.

You might cause system coruption if you use this button at the wrong time.

The button will only work if corectly connected to yout mainboard.

Thats my understanding of the topic.
Feel free to corect me.