In response to an iPhone 7 freezing issue I'm having, it was suggested to try a hard reset (holding power + volume down for 10 seconds for iPhone 7 or holding power + home on older iPhones).
This got me wondering what an hard reset actually does. After searching around online, I've sound some that say it is just a hard power-off (isn't this what holding just the power button does?) and others mentioning something about a library being rebuilt. Overall, many, at least from several years ago, cited it as a cure-all for various phone issues.
Does anyone know what a hard reset does? I'm envisioning something analogous booting a Mac in safe mode or doing a PRAM/SMC reset on a Mac, but online searches so far are leaving me unsure.