This is a paid application to enable customizing the behavior of all your Apple input devices (remotes, keyboards, mice, touchpads, etc.) It's definitely worth the money for a lifetime license. Older versions that don't support current MacOS are also available for free from the software publisher that purchased BetterTouchTool from its original creator.
It adds some important capabilities:
If you don't care about the input device stuff, the window snapping feature is available as a free app from the publisher.