What are wash marks?
Wash marks are light scratches caused by the process of washing your car, they are to be found on almost every car and almost impossible to avoid.
Paintwork is fairly soft, and is certainly softer than much of the dirt and grit that makes your car dirty. Washing the dirt off without letting it scratch against your paintwork is practically impossible, even when using washing techniques specifically designed to reduce wash marks.
Most people don't wash their car using special techniques, and in this day and age, probably don't wash their own car, they will put it through a car wash. Many of the newer car washes are soft-wash or touchless washes, but even these can cause fine scratches which build up over time and will eventually appear like cobwebs over your car when seen under harsh light.
The good news is that even though you have these scratches, if the car was washed somewhat gently, the scratches should be very light and should polish out.
More serious issues occur when your car has been washed using bad practices. So if somebody in a fluorescent bib, with a bucket on a trolley, approaches you in a supermarket car park, and asks you if you want your car cleaned, politely tell the to stroll on.
These outfits often use techniques such as washing five cars with the same dirty bucket of water, using a sponge that keeps getting dropped on the ground, or failing to rinse the larger particles of grit off the car before vigorously wiping it over with a sponge can cause significant damage. It's also worth noting that some of the more cost-effective places where you can get your car cleaned, make the operation more efficient by using detergents which are so caustic that they can etch paintwork and burn plastic and rubber. These would also be considered wash marks.