The document discusses the different types of conditional sentences in English:
- Zero conditional sentences are used to talk about things that are always true with a present simple structure.
- First conditional sentences are used to talk about real or possible situations with an "if" clause in the present simple and a main clause with "will + infinitive".
- Second conditional sentences are used to talk about unreal or impossible things with an "if" clause in the past simple and a main clause with "would + infinitive".
- Third conditional sentences are used to talk about the past with an "if" clause in the past perfect and a main clause in the "would have + past participle" structure. Examples are provided