A men's-specific cycling jersey is patterned for male body proportions — typically broader shoulders, a longer torso, and a different chest shape compared to women's cuts. The fabric panels, seam placement, and overall silhouette are all engineered to fit the male frame comfortably while you're in a riding position.
If you're a male rider, a men's-specific jersey will generally give you the best fit, especially in race or club-cut styles where a close, aerodynamic fit matters. The shoulders won't pull or bunch, and the torso length will properly cover your lower back when you're leaned over the handlebars.
Women riders should avoid men's jerseys, as the proportions won't align well — the shoulders will be too wide, the torso too long, and the chest area won't accommodate properly. Women's-specific jerseys offer a much better on-bike experience and have improved dramatically in recent years.