Condition and result can be interchanged.

In some cases, the if can be replaced with other words, like when or in case.

Unless can be used to negate the if. Unless = if + subject + don't/doesn't.

Zero conditional

A truth or a fact.

If you heat water to 100C, it boils

Situation: Present simple (heat). Result: Present simple (boils).

First conditional

Probable/possible future situations. A possibility that something will happen in the future.

If it doesn't rain I will go to the beach. If I study hard, I will pass the exam.

Situation: Present simple (doesn't rain, study). Result: Future simple (will go, will pass).

Second conditional

Unlikely/hypothetical general/present/future.

If I were smarter, I wouldn't have to study so hard. If I won the lottery, I would buy a car.

Situation: Past simple (were, won). Result: would + infinitive (wouldn't have, would buy).

Third conditional

Hypothetical past situation with past result.

If I had studied better, I would have passed the exam.

Situation: past perfect (had studied). Result: would/could + have + past participle (would have passed).

Mixed conditional

First variant

Hypothetical present situation with past result.

If I won the lottery, I would have gone to Hawaii with you last month.

Situation: Past simple (won). Result: would/could + have + past participle (would have gone).

Second variant

Hypothetical past situation with present result.

If I had eaten an hour ago, I wouldn't be hungry now.

Situation: past perfect (had eaten). Result: would + infinitive (wouldn't be).