A guide is someone who shows you the way. You'd be lucky to have a kind older sibling to act as your guide through middle school, giving you advice and helping you figure out the school and social scenes.
A guide often leads tourists through a city, taking them to important sites, or assists a group of mountain climbers. Another kind of guide is a book of helpful instructions about what to see in a particular country, how to get along with your teenager, or the best way to grow orchids. When you guide people, you help them find their way, whether it's through the New York subway system or through the steps of building a campfire.