Our solar system is pretty sparkling clean when it comes to dust. That isn't necessarily the case elsewhere, as many other stars are surrounded by thick disks of debris. These might actually be the perfect places to find Earth-like planets.
All planets are vast clumps of dust and gas packed together by gravity. If there's lots of material, a gas giant is the result. If there isn't much material, you get a rocky planet. At least, that's what we thought.