Displays the frame rate in the main window’s title bar. At 30 frames per second an animation looks smooth. At 60 frames per second it looks perfect. At more than 60 frames per second it looks… exactly the same, because 60 frames per second is (roughly) the rate at which your computer refreshes the display on your monitor. In other words, even if the program were busily computing 180 frames per second, ⅔ of those frames would never make it to the screen.
There’s no practical advantage to displaying the frame rate, so enable it only if you’re curious.