The document discusses different types of mixed conditionals and how to use wish clauses. There are two types of mixed conditionals - third/second conditionals which refer to a past condition and present result, and second/third conditionals which refer to a present condition and past result. Wish clauses can be used with the simple past to express wishes for present situations, the past perfect to express regrets about past situations, or would/wouldn't plus the infinitive to criticize and want to change someone's habitual behavior.