Most people think that dust is just unnecessary molecules flying around. But as it turns out, dust is matter and it's important too.
Dust is all around us, but many may not know what it actually is. Dust contains particles of dirt or other solid matter. This matter is light enough to be carried by the wind and can come from, among other things, dead plants, volcanic sand, ashes, and soot.
Additionally, dust can actually be beneficial. The colors of the sky at dawn need a great amount of dust in the air to show the colors of sun sets hours later. For this to happen, colors of rays from the sun bend in different directions. Specifically, dust and water vapor particles bend the red rays of the sun to an angle at which they are the last to vanish from sight. This is why sunsets typically appear red.
Rain, unusual as it might seem, also depends on dust. The water vapor in our atmosphere, every raindrop starts as specks of dust. So do the tiny drops of water that make up clouds.
Even if you don't want dust around your house, next time you see it, stop to think about all that it does for our Earth!
[Source: The Big Book of Tell Me Why]