Torii are the shinto symbol.
Most shrines have at least one.
Inari shrines can have very many.
The origein of the torii lies in darkness, the word itself means "bird-there" in japanese.
there are many different types of torii.
All mark the entrance to a sacred space.
Sometimes you will pass 3 or more like in Meiji shrine,
as you walk towards the sanctuary, each torii lifts your soul to the divine.
Torii symbols are often used when referring to shinto or Japan in general.