The document discusses different types of conditional clauses in English. There are three main types:
Type I refers to possible future actions and uses the present tense in the if-clause and would + verb in the main clause.
Type II refers to hypothetical or unlikely present actions and uses the past tense in the if-clause and would + verb in the main clause.
Type III refers to impossible past actions and uses the past perfect in the if-clause and would have + past participle in the main clause.