Guide

noun

1. Someone who guides, especially someone hired to show people around a place or an institution and offer information and explanation.

   "The guide led us around the museum and explained the exhibits."

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.