The first conditional and second conditionals talk about the future. With the third conditional we talk about the past. We talk about a condition in the past that did not happen. That is why there is no possibility for this condition. The third conditional is also like a dream, but with no possibility of the dream coming true.
Last week you bought a lottery ticket. But you did not win. :-(
Last week you bought a lottery ticket. But you did not win. :-(
condition | result | |
Past Perfect | WOULD HAVE + Past Participle | |
If | I had won the lottery | I would have bought a car. |