You pick an artist, leave a request (including refs), and they can either accept or reject it. The main gimmick is that there is no communication after the initial request, as in it's prohibited. The artist will have specified what they're willing to accept (including NSFW or nah).I've never used skeb. Has anyone here used it that could explain the process and how much it usually costs?
Main advantages are extremely competent auto-translation, little to no fuss, and the fact that mainly Japanese artists use it. It's no good for anything that you need to get just right, and communication even if you're unhappy with the result is still prohibited. If you have a general idea like "Please draw Hexa smoking a huge blunt on the Joe Rogan show", it's honestly amazing compared to the rigamarole and mental illness you often have to deal with when commissioning western artists.
Price varies a lot by artist, but I'd say it's cheaper than western artists from first world countries in general. It makes it easy to discover artists and find people with cool and unique styles.
Overall, it makes it amazingly easy to commission fun little things. Great product.