Imagine that you are watching an hourglass with sand slowly running through it. At first, you might see the hourglass as a solid, permanent object with a clear identity. But as you continue watching the sand trickling down, you start to realize that the hourglass is not a fixed, unchanging object. In fact, the hourglass is constantly changing as the sand slowly drains from the top to the bottom bulb.
As you watch the sand falling, you start to recognize the emptiness of the hourglass. You see that the hourglass is merely a collection of parts - the two connected bulbs and the narrow middle segment. Without the sand, the hourglass doesnt serve any purpose.
Through this realization, you begin to see that all things are empty of inherent existence, including yourself. You start to see that everything changes and is dependent on causes and conditions, just like the sand falling in the hourglass. This understanding can lead to a deeper sense of freedom, as you let go of clinging to a fixed sense of self and begin to see the world with greater clarity and wisdom.