A non-helmet fixed hood is built specifically for riders who skip the helmet and ride with just a beanie or bare head. It's permanently attached and has a lower, sleeker profile than helmet-compatible hoods, so it won't feel oversized or baggy when worn without a helmet underneath.
The main advantage is comfort and style—it sits closer to your head, looks cleaner, and eliminates the excess material you'd have to cinch down with a helmet-sized hood. You'll typically find this option on casual or fashion-focused snow jackets rather than technical gear.
The big catch: if you ever decide to start wearing a helmet, this hood won't fit over it. Since most modern snow jackets are built with helmet compatibility, non-helmet hoods are becoming less common. Also consider that even if you don't wear a helmet now, a helmet-compatible hood worn without one still works fine—you just cinch it down—giving you more flexibility if your preferences change.