The document discusses the use of the modal verb "should" and its forms. It notes that "should" can be used to give advice, express obligations or likelihood, and provides examples of its use in affirmative, interrogative, and negative sentences. Key uses of "should" include giving recommendations, expressing expectations, and describing obligations in a polite way. The negative form is "shouldn't" or "should not", used to advise against something. Questions with "should" seek advice or suggestions.