guide

(noun): Someone who guides, especially someone hired to show people around a place or an institution and offer information and explanation.
(noun): A document or book that offers information or instruction; guidebook.
(noun): A sign that guides people; guidepost.
(noun): Any marking or object that catches the eye to provide quick reference.
(noun): A device that guides part of a machine, or guides motion or action.
(noun): A spirit believed to speak through a medium.
(noun): A member of a group marching in formation who sets the pattern of movement or alignment for the rest.