No such thing as a dumb question on this forum.
Basically it's a soft bedrock that can be easily eroded by wind blown sands and chips of the same rock. The wind carves out deep channels and troughs that usually align with the prevalent wind direction. We have them here on Earth and also on Mars.
Here's a link to the best description I've seen and it also contains some great photographic examples
https://www.smithsonianmag.com/smart-news/what-yardang-180951461/