The document discusses several structures using past tenses to express different meanings and situations. It explains that "wish + past simple" is used to talk about things in the present/future that are impossible or unlikely. "Wish + past perfect" expresses regret about past events or actions. "Would rather + subject + past tense" indicates preference. And "It's time + subject + past tense" means that something needs to be done now or soon. Examples are provided for each structure.