Conjunctions are words that join other words, phrases, or clauses. There are two main types of conjunctions: coordinating conjunctions and correlative conjunctions. Coordinating conjunctions connect words, phrases, and clauses of equal value using words like "and", "but", and "or". Correlative conjunctions connect words, phrases, and clauses of equal value by working in pairs like "both...and" or "either...or". The document also discusses interjections, which are words that express emotion and interrupt sentences, such as "ouch" or "wow". Interjections are usually followed by commas or exclamation points depending on the level of emotion.