The superlative is used when stating that something is the best, the most beautiful, the tallest or the least expensive.
The words in French are:
An adjective or an adverb needs to come after le/la/les plus or le/la/les moins and make the adjective agree. For example:
Use le plus, la plus, les plus or le moins, la moins, les moins and the correct form of the adjective, depending on whether you're describing something that is masculine, feminine, singular or plural.