Answer first
The Norwood scale grades male pattern hair loss from stage 1 (no recession) to stage 7 (only a band of hair at the sides and back). Knowing your stage helps you and your consultant choose sensible goals, from scalp care and topicals at early stages to hair systems or SMP for wider areas.
Early stages (1 to 3)
Temple recession and a slightly higher hairline. Often the best time to start a routine.
Middle stages (3 vertex to 5)
Crown thinning joins the frontal recession. Coverage options become more useful.
Advanced stages (6 and 7)
Large bald areas. Hair systems and SMP give the most visible change.
Questions
Can I tell my stage myself?
Roughly, using photos; a trichoscope check is more accurate.
Does everyone move through all stages?
No; many people stay at an early stage for years.