3D Touch is a feature that's been around since the 2015 release of the iPhone 6s, and it's become an integral gesture system on all of Apple's latest iPhones.
Though it's been around for a while, there are several hidden and less obvious 3D Touch gestures that you may have forgotten or might not be aware of, especially if you don't use the feature often. Video below covers 3D Touch Cursor, Control Center, Prioritizing App Downloads, Previewing, Sharing, and Saving Photos, and Third-Party App Shortcuts.
MacRumour's recent YouTube video demonstrates some of the most useful and lesser known 3D Touch gestures.