The second conditional is used to express an unreal or improbable condition and its result. The past forms are used to show this is different from reality.
The condition is unreal because it is different from the facts that we know. We can always say ‘But…..’
If I were Prime Minister, I would lower taxes for all the people. /But I’m not Prime Minister./
If I had a tattoo, I would have a little butterfly on my shoulder. /But I don’t have a tattoo./
What would you do if you saw a ghost? /But I don’t think you’ll see a ghost./
In the if clause we use if+Past Participle. In the main clause we use would+infinitive /verb stem/.
If I had more money, I’d buy a washing machine
If we didn’t have to, we wouldn’t work so hard.
If she knew the answer, she’d tell us.