. there are several styles of torii [see pict]
(shinmei torii, mihashira torii, ...);
what they all have in common
is providing a door frame to walk under,
. sometimes there is some brief fencing,
but instead of the gates going parallel with the frame,
they are parallel with the door's path,
reminding of the handrails for a creek bridge .
. the purpose of the gate is to
suggest you are leaving our world
and entering the spirit world
where the Shinto shrines are meant to be at .
. often a wooden red torii
marks the entrance to the shrine grounds,
then a stone torii marks the actual shrine area.