The document discusses conjunctions, which are words that join words or groups of words. There are two main types of conjunctions: coordinating conjunctions and subordinating conjunctions. Coordinating conjunctions connect words, phrases, and clauses of equal value, such as with "and", "or", and "but". Subordinating conjunctions introduce dependent clauses that cannot stand alone as a sentence and are dependent on the rest of the sentence for their meaning, such as with "since", "because", and "while". The document provides examples and exercises to illustrate the different types of conjunctions.