Intonation refers to the variation in pitch when speaking. There are two basic intonation patterns in English: 1) Falling tune, where the voice falls at the end of a statement, used for short sentences, questions with question words, and commands. 2) Rising tune, where the voice rises at the end, used for encouraging statements, yes/no questions, questions showing interest, and sentences ending with "please". Understanding intonation helps convey feelings, moods, and the type of statement.