Apple's new Force Touch Trackpad comes with Force Click.
Force Click is a convenient way to invoke secondary actions with what is, in essence, a secondary, "deeper" press into the trackpad. Apple currently ties Force Click into the Quick Look, Look Up, data detector, and detail view functions, as well as a few extras. That means you can generally go deeper just by ? wait for it ? going deeper. Here are all the basics!
Full story from the iMore Blog...