Wind animation is a good way to add some subtle life to your animations, by making the trees sway back and forth as if in the wind.
Alternatively, you could turn up the settings, and have the trees being rocked by strong gales, and add a sense of power to animations.
Note that the trees will always rotate in the relative Y direction, so if the camera rotates around them, they will always rotate the same way.
There are a few settings you can change to customise the look of the wind animation:
Amount: This is the influence that the wind animation has on the trees. At zero, the trees will not move at all, and at one, they will sway fully.
Lean: The amount to offset the rotation of the trees. Setting a high value is good for very strong winds where the trees are being blown at an angle.
Speed: The speed of the animation. Higher values make the animation go faster, and lower values make it go slower.
Randomness: A random amount to vary the rotation of each tree by. This helps to break up fake looking patterns in the trees.
Pattern scale: The animation is driven by a large noise texture so that trees rotate similarly to their neighbours. This changes the scale of that noise texture.
This shows what each setting does: