In English you can find three different kinds of conditional sentences. They're known as First, Second and Third Conditional Sentences. There's no reason for you to get bewildered. Let's take a look:
FIRST CONDITIONAL
Structure: IF (Simple Present) + Will / Can / May
Use: when you talk about possible future actions or an action that relies on another.
IF I have money I will / can / may buy a new house.
SECOND CONDITIONAL
Structure: IF (Simple Past) + Would / Could / Might
Use: when you talk about the consequences of unreal actions in the present.
IF I had money I would / could / might buy a new house.
THIRD CONDITIONAL
Structure: IF (Past Perfect) + Would / Could / Might HAVE + Past Participle
Use: when you talk about the consequences of unreal actions in the past.
IF I had had money I would / could / might have bought a new house.
There are also three other things you must know about them:
a) First Conditional Sentences may be represented by IF (Simple Present) + Imperative, when giving advice, making suggestions or recommending something. For instance:
- If you are sick, go home now!
- If you are running out of money, don't spend more than you can afford.
b) The structure of conditional sentences may be broken and the inversion will present the sentences:
- I will / can / may buy a new house IF I have money.
- I would / could / might buy a new house IF I had money.
- I would / could / might have bought a new house IF I had had money.
c) There are also Zero Conditional Sentences, which means the action described has a 100% chance of happening. It uses both sentences in the simple present tense.
- If the water boils, the temperature is 100°C.