They're all just skis. There is no magic formula of rainbows and unicorn farts that make a ski a women's ski.
The difference is generally the women's ski market is heavily focused on intermediate and beginner's gear meaning theres a ton of great options for women who are just learning to ski. However once a women is confidently ripping the whole mountain the options are pretty limited. Most companies high performance women's gear is a softer and lighter version of the men's gear and comes in shorter lengths giving women less variety when choosing a ski. This means that many ripping women choose to turn to so-called men's skis.
Now there's physically no problem with a woman shredding on a "man's" ski - as I said before... they're all just skis, but it's a pretty shitty feeling to think that the entire industry surrounding the sport you're the most fucking passionate about seems to think you're not good enough for their high end gear.