Impress: What's the meaning of that little star with little mouse pointer?

In Impress there’s a list of the slides in a presentation on the left hand side of the screen, showing thumbnails of the slides.

On some of the slides, there’s a little yellow stark/asterisk symbol with a little mousepointer symbol to the left of the thumbnail: image description

What’s the meaning of that symbol?

There is an object on the slide, which has an animation effect.