Zero · First · Second · Third
We use the zero conditional to talk about things that are always true — facts, habits, or natural laws. IF and WHEN are interchangeable in this structure.
Use the first conditional when the situation is real or possible and the result is likely to happen. The IF clause is in the present — never use 'will' after 'if'.
Use the second conditional when the situation is imaginary, unlikely, or impossible — now or in the future. After 'If I', use 'were' (not 'was') in formal English.
Use the third conditional to imagine a different past. The situation did NOT happen.
would have → certain imaginary result · might have → less certain · could have → unused ability.