A punctuation mark is a symbol used in writing to clarify meaning and indicate pauses or stops in sentences. Common punctuation marks include the period, comma, question mark, and exclamation point. Each mark serves a specific purpose, helping readers understand the structure and flow of the text. Punctuation marks are essential for effective communication, as they can change the meaning of a sentence. For example, the difference between "Let's eat, Grandma!" and "Let's eat Grandma!" highlights how punctuation can alter the message. Proper use of punctuation enhances readability and ensures that the writer's intent is conveyed clearly.