Punctuation is used to separate sentences and parts of sentences to make their meaning clear. The main punctuation marks are the period, question mark, exclamation mark, comma, colon, semicolon, parentheses, hyphen, apostrophe, quotation marks, and dash. Each punctuation mark has specific uses, such as commas separating elements in a list, periods ending sentences, question marks following questions, and quotation marks enclosing direct quotes.