According to Sekien's commentary in the "Hyakki Tsurezure Bukuro," the Burabura looks like a lantern light, however, it is actually believed to be a Kitsune-bi (a Japanese will-o'-the-wisp).
『百器徒然袋』中にある石燕の解説文によれば、外観は提灯の火だが、実体は狐火とされている。