Sometimes we call them 'if clauses'. They describe the result of something that might happen (in the present or future) or might have happened but didn't (in the past) . They are made using different English verb tenses.
Zero conditional If + present simple, present simple.If you heat water to 100 degrees, it boils.
First conditional if + present simple, ... will + infinitiveIf it rains tomorrow, we'll go to the cinema.
The Second Conditionalif + past simple, ... would + infinitiveIf I had a lot of money, I would travel around the world.
The Third Conditionalif + past perfect, ... would + have + past participleIf I had gone to bed early, I would have caught the train.