The document discusses the four main types of conditional sentences in English:
- Type 0 (present simple) - factual statements that are always true
- Type 1 (present/future) - possible outcomes if a present or future situation occurs
- Type 2 (past) - hypothetical situations that are unlikely or impossible
- Type 3 (past perfect) - hypothetical past situations and their consequences
Examples are provided for each type of conditional sentence.