The naginata is one of these swords/polearms that leaves everyone perplexed when they first see it. While it looks like a polearm, it isn't exactly one... And while it's a type of sword, it isn't exactly a sword... It's a mix of both.
In feudal Japan, the naginata was primarily a Samurai sword
, as it was used by this near-royalty class of people. It was also employed by the ashigaru (foot soldiers) and the sōhei (warrior monks).
Yet, it's most legendary use was by the Onna-musha, or female samurais. If you have the time, you can look at some of the artwork online, it's truly impressing. Usually mounted on a horse, these fearless women defied gravity and fought alongside the Samurai in times of need... holding a naginata most of the time. Its length made it easy for the Onna-musha to fight better equipped men. It's simply because they could better deal with distance and thus gain an advantage over the men's physical force.
In addition to being used to smash, stab, and hook opponents, naginata are frequently spun and twirled. This is done to proscribe a vast radius of reach due to the relatively balanced center of mass of the weapon.