The document defines key grammatical terms such as sentences, clauses, phrases, subjects, predicates, and parts of speech. It explains that a sentence contains a subject and a predicate, with the subject being what is being talked about and the predicate containing a verb stating what the subject is or does. Clauses can be independent, containing a complete thought, or dependent, not expressing a complete thought. Phrases are grammatical units within clauses or sentences that do not contain both a subject and predicate. Various terms are given examples and classifications.