A men's cycling shoe is built on a last (the foot mold used to shape the shoe) designed around typical male foot proportions. This generally means a wider forefoot, higher overall volume, and a larger heel-to-ball ratio compared to women's-specific models. For most male riders with standard to wide feet, a men's shoe will offer the best fit right out of the box.
That said, gender labels aren't absolute rules. Some women with wider feet may find men's shoes more comfortable than women's models, which tend to run narrower. The most important thing is how the shoe actually fits your foot—especially heel retention and whether you feel pressure points or excessive sliding. If you're a woman considering a men's shoe, keep in mind that sizing scales differ, so you'll typically need to size down about 1.5 sizes from your women's number.