A Guide

1. Someone who guides, especially someone hired to show people around a place or an institution and offer information and explanation.
2. A document or book that offers information or instruction; guidebook.
3. A sign that guides people; guidepost.
4. Any marking or object that catches the eye to provide quick reference.
5. A device that guides part of a machine, or guides motion or action.

• A blade or channel for directing the flow of water to the buckets in a water wheel.
• A grooved director for a probe or knife in surgery.
• (printing, dated) A strip or device to direct the compositor's eye to the line of copy being set.

6. (occult) A spirit believed to speak through a medium.
7. (military) A member of a group marching in formation who sets the pattern of movement or alignment for the rest.