There are three main types of conditional patterns in conditional sentences: Pattern A is used for probable conditions, Pattern B is used for improbable conditions, and Pattern C is used for imaginary conditions. Pattern A uses present tense in the if-clause and future tense in the main clause. Pattern B uses past tense in the if-clause and would/should + verb in the main clause. Pattern C uses past perfect in the if-clause and perfect conditional ("would have" + past participle) in the main clause.