zero conditional

I always feel miserable when it rains.

first conditional

If it's nice weather tomorrow, we'll (we will) go and have lunch in the park.

second conditional

If I had more time, I'd (I would) travel more.

third conditional

If I'd (I had) known you were coming, I would've (would have) waited for you.

If you go to England, you will improve your English.

We use present simple in the if-clause.

If I find his address, I will send him the letter.

The main clause has will, which expresses certainty in the future.

I'll tell him as soon as I see him.

We use present simple in the if-clause.

If I had enough money, I would buy a new computer.

We use the past simple (I had) in the if-clause when we are talking about something which is unlikely to happen or an imaginary situation.

If you didn't hurry so much, you would feel more relaxed.

The main clause has would + infinitive.

If I had asked him, he would have helped me.

In the if-clause we use the past perfect (had + past participle).

If you had spoken to my mother, she would have told you where I was.

The main clause has
would + have + past participle.