The Action button, which could be similar to the Apple Watch Ultra's Action button but with more phone-focused options, is expected to be a new physical button on the next-generation Pro iPhone models that replaces the Ring/Silent switch. The Action button would allow users to quickly access various functions and settings without necessarily unlocking the device or navigating to an app.
From https://www.macrumors.com/2023/07/26/ios-17-beta-action-button-iphone-15-pro/
Ctrl+R to search your bash history. I hate how long I went without knowing this, so I've always got to spread the word about it.