A jersey with moderate reflective elements typically has reflective strips across the back pockets and sometimes on the shoulders or side seams. These are placed where they matter most—catching car headlights from behind and the sides when you're riding in traffic.
For most commuters and riders whose training rides occasionally stretch into dusk, moderate reflectivity hits a sweet spot. You get solid visibility from the angles where cars approach you, without the full hi-vis look that some riders find too bold for group rides or café stops.
If you're riding on well-lit roads during dawn or dusk, moderate is generally sufficient. However, if you regularly ride after dark on unlit roads, consider stepping up to extensive reflective elements or adding a dedicated reflective vest for those conditions.