There are several grammatical resources to express unreality status of counterfactuals, including mode selection and the tense. In turn, different disciplines have studied the counterfactual expression, whose main theoretical assumptions are discussed in the current article. We analyze the prototypical counterfactual expressions like "If I had won the lottery, I would have bought a Mercedes Benz" in comparison with other tense forms that express impossibility or probability as in the case of prefactuals.