Not sure exactly how to warm up before practicing piano? Check out Robert Estrin's video and my series of musician stretches.
This finger exercise is one I learned at one of my early piano lessons, many moons ago. It's a hand exercise to strengthen those musical fingers, especially our very weak finger #4.
I detested it during those early piano practices, but I must say, my Finger #4's are better because of it. My students and I have dubbed it "Finger Push Ups":