As the name suggests, swipe to capture allows you to take a screenshot by swiping your palm across the screen. Fortunately, the OneUI is very lenient about the type of swipe. It doesn’t have specific speed, pressure, or even direction criteria. All it requires is for you to swipe across at least 50% of the surface area on the display.
The display responds with a dramatic effect and shows you your screenshot in the bottom left for a second or two. You can tap on it and choose an app (Gallery, Google Photos, etc.) to view it.
iPhone’s equivalent of this is double tapping the back of your phone. There are much stricter guidelines on where you’re supposed to tap, and it often doesn’t register your action when it’s off by even less than an inch. I’ve also lost count of how many accidental screenshots I’ve taken on my iPhone because I mindlessly double-tapped its back. I stick to my customized shortcut on the Assistive Touch for screenshotting on my iPhone since that’s much more reliable.