This document discusses the zero, first, second, and third conditional tenses in English. The zero conditional is used to talk about results that always happen, using the present simple. The first conditional talks about real possibilities in the present or future, using "if + present simple + will." The second conditional discusses unreal possibilities, using "past simple + would." The third conditional is for talking about things that cannot be changed because they are in the past, using "past perfect + would + have + past participle." Examples are provided for each conditional.