The document discusses the second and third conditional tenses in English grammar. The second conditional describes an unreal possibility or dream about the future, using the past simple tense for the conditional clause and "would" for the result. For example, thinking about winning the lottery without a ticket. The third conditional describes a condition in the past that did not happen, making the possibility impossible now. It uses the past perfect tense for the conditional clause and "would have" for the result, like thinking about winning the lottery when a ticket was not actually bought.