A more thorough explanation:

A thesaurus is a type of reference book that lists words and their synonyms (words that have similar meanings) and antonyms (words that have opposite meanings).

For example, if you look up the word "happy" in a thesaurus, you might find synonyms like "joyful," "pleased," and "content," and antonyms like "sad," "unhappy," and "miserable."

The purpose of a thesaurus is to help writers find the right word to express their ideas more precisely and creatively. By using a thesaurus, writers can avoid repeating the same words over and over again and add variety and depth to their writing.