guide
When used as a noun for a person, 'guide' refers to someone with expert knowledge of a place. When used as a noun for a book, it is often called a 'handbook'. As a verb, 'guide' can be used physically (leading someone by the hand) or metaphorically (giving advice to help someone make a decision). Note that while 'guide' is common in both American and British English, the types of guides (like 'tour guide') are universal.
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Meanings
A person who shows the way to others, especially one employed to actually accompany strangers in unfamiliar territory.
"Our mountain guide led us safely through the pass."
A book or other document providing information or instructions on a particular subject.
"I bought a study guide to help me prepare for the final exam."