This document discusses different types of conditional sentences in English, including real and unreal conditionals. It explains the verb tenses used in if clauses and main clauses for both real and unreal conditionals. For real conditionals, it notes that present, past, and future tenses are used as in other sentences. For unreal conditionals, it explains that past tenses are used in if clauses to talk about present or future situations, and "would" is used in main clauses. It also discusses mixed tenses that can be used and exceptions. The document provides examples to illustrate the different conditional structures.