Almost everyone has used a dictionary at some time or another:
A dictionary is a reference book that contains the pronunciations, meanings, part of speech, history, and correct spellings of most of the words of a language.
A glossary is a specialized vocabulary list, and usually does not contain any other information except for the definitions of the words.
A lexicon is similar to a glossary, but the words, along with their definitions, are arranged in alphabetical order. “Lexicon” is also considered to be a more formal and less-used term for a “dictionary”.