Guan is broad term for any type of hat in Hanfu headwear. It tends to cover the full top of the head; for Hanfu headwear that only covers the topknot, see Xiao Guan.
Please see the subtypes and use them instead, as guan is unspecific.
The Guan was typically a formal form of headwear which was worn together with its corresponding court dress attire. There were sumptuary laws which regulated the wearing of Guan; however, these laws were not fixed; and thus, they would differ from dynasty to dynasty. There were various forms and types of Guan.
As the character Guan (冠) is of a homonym another Chinese character pronounced Guan (官) which literally means official; the Guan (冠) became the symbol of officials. Note, this should not be confused with futou which essentially replaced the Guan as Chinese court wear around the Tang dynasty (but continued to be worn by Confucian literati until the Ming dynasty, where it became the exclusive headwear of the royal family).
Subtypes
Fengguan - Women's headgear for official events, ceremonies, and weddings
