Popcorn ceilings or textured ceilings are very common as they help to hide imperfections in the ceiling drywall, which otherwise can be very evident.
Dust and small spider webs tend to get caught on these rough surfaces. Although they may not be entirely evident at a glance, even in the cleanest homes, most ceilings can accumulate noticeable dust after as little as a year.
The easiest way to clean this type of ceiling is using a vacuum with a soft brush attachment. Be very gentle so as not to knock off the texturing. Follow a methodical pattern to be certain you cover the entire surface of the ceiling. Even if you are very careful, don’t be alarmed if some texturing falls off.
If the ceiling is stained from a water leak, or pop, champagne or food being sprayed, there is no way to clean it, however there are products that allow you to spot spray paint an area with a matte off white color which unfortunately will never be an exact match, but it will be close for an aged ceiling.