Conditional
Third conditional structure
If + past perfect + would + have + past participle
Zero conditional structure
If + present simple + present simple or infinitive
Second conditional structure
If+past simple+ would+ infinitive
First conditional structure
If+present simple+will+infinitive
Third conditional use
It's used to describe a situation in the past that didn't happen, and to imagine the results of this situation.
First conditional use
It's used to talk about things which might happen in the future. It describes possible things which likely come true.
Zero conditional use
It's used when the result will always happen.
Second conditional use
(Imaginary future) if the situation is possible, but not necessarily probable, if it is more hypothetical we use the second conditional