Force Touch allows the device to tell a tap from a press and provides for a wider array of input options over the current technology. Rather than actually detecting pressure applied by the fingers, it looks like it will be measuring differences in the size of the area the finger touches in order to infer pressure.
You might use the technology to make lines darker with increased force or pop up a “right click” screen with pressure. Add this to multi-finger gestures and it multiplies the input options.
The current 13” MacBook Pro, released in March, the upcoming 12” MacBook and the Apple Watch will also have this technology. The MacBooks implement Force Touch on the touchpad, but the Apple Watch and the new phone will implement it on-screen. (The MacBooks also have a haptic feedback feature that can feel like a click when you press harder.)
Have you used this technology yet on one of the new MacBook Pros? What do you think?