Try this experiment...
- Find a room with a white wall (or any kind of white background)
- Tape a small piece of white paper on the wall (say about the size of a quater)
- Take another small piece of paper, make it black by writing on it with a pen, and also stick it on the wall
- Go as far away from the wall as possible and look at the pieces of paper.
- Which piece of paper is easier to see?
Pieces of dust are so small, that they are generally difficult for our eyes to see. However, when exposed to bright sunlight, the bright light is reflected off the dust particals making them appear very bright against a dark background.
On a side note, all of the matter on the planet was originally created in the stars many billions of years ago. So, I guess you can say the sun (or rather, some other star) creates dust.