If clause type 1 is used to talk about real possibilities and their probable results in the present or future. The structure of this type of conditional sentence is "if + present simple, will + base verb". For example: "If it rains, I will stay at home." In this example, the possibility of rain is real, and the result of staying at home is probable.
If clause type 2 is used to talk about unreal or improbable situations in the present or future and their hypothetical results. The structure of this type of conditional sentence is "if + past simple, would + base verb". For example: "If I had a lot of money, I would buy a big house." In this example, the possibility of having a lot of money is unreal, and the result of buying a big house is hypothetical.
If clause type 3 is used to talk about situations in the past that did not happen and their imaginary results. The structure of this type of conditional sentence is "if + past perfect, would have + past participle". For example: "If I had studied harder, I would have passed the exam." In this example, the possibility of studying harder is unreal, and the result of passing the exam is imaginary.
