Punctuation includes marks such as periods, commas, and apostrophes that are used to separate sentences and clauses and make the meaning clear. Capital letters should be used at the beginning of sentences, for proper nouns like names and titles, and for days and places. Commas are used to separate independent clauses and follow introductory phrases. A period ends declarative sentences and is used with abbreviations. An apostrophe is used for contractions and to show possession. Punctuation helps organize sentences and clarify meaning.