Pinch gripping involves squeezing the extended fingers towards the thumb without flexing individual digits, such as you'd experience holding a textbook.
Most strength athletes use plate pinches (holding two 25 or 45 pound plates together), but there are alternatives. For example, using two dumbbells allows you to have access to a greater range of weights. That makes it much easier to progress in smaller increments.
You multitaskers out there will love this movement as it allows you to work the rectus abdominis, the obliques, and the serratus at the same time. Too bad the rest of your life isn't as efficient.
When you have knee or shoulder issues, this is a good alternative to a standard squat. This is the touch-and-go version with chains for overload at the top.
I remember lying on the incline bench. It was an "old school" incline bench: long, straight, and red, with footpads at the bottom so you're literally locked in from heel to shoulder for every rep.