The step option allows you to change the spacing between images in the animation. For example, a step of five means that you will be looking at every fifth possible image. By choosing a larger step you can see more of the previous 24 hours. Most of the time, frames are generated every minute.
It is possible to view temperature, humidity, insolation (sunshine), uv index and wind speed and direction. The wind speed movie is perhaps the most difficult to interpret since the wind field is highly variable at the short time scales used here. The insolation and uv index fields are blank at night (there's no sunlight).