"Animated Zooming" governs the behavior of yEd's "Zoom In", "Zoom Out", "Reset Zoom", and "Fit Content" actions.
If "Animated Zooming" is disabled, these actions will change the zoom factor in the editor area in one frame.
If "Animated Zooming" is enabled, these actions will use a smooth animation to change the zoom factor.
To understand the difference in behavior, create a diagram with one node, click reset zoom (the third button shown above), zoom out several steps (the second button shown above), then click reset zoom again.