CONDITIONAL

1. The Zero Conditional (Type 0)The zero conditional is a structure used for talking about general truths, or scientific facts -- things which always happen under certain conditions.

A zero conditional sentence consists of two clauses, an "if" clause and a main clause (note that most zero conditional sentences will mean the same thing if "when" is used instead of "if"). For example:
If the "if" clause comes first, a comma is usually used. If the "if" clause comes second, there is no need for a comma.
The simple present tense is the tense use in both clauses. Examples:
If you cross an international date line, the time changes.
Phosphorus burns if you expose it to air.

2. First Conditional (Type I)

The first conditional (also called conditional type 1) is a structure used for talking about possibilities in the present or in the future.Type 1: if + present + future.
Example:
If I have the money, I will buy this car.
If it's sunny, we'll go to the park.
Peter will be sad if Susan leaves.
If you cook dinner, I'll wash the dishes.
Among other variations the structure if + present + present is also possible. It is used when the results are habitual or automatic. Example: If a commodity is in short, supply prices tend to rise.

3. Second Conditional (Type II)

The second conditional (also called conditional type 2) is a structure used for talking about unreal situations in the present or in the future.Type 2: if + past + conditional
Example:
If I had the money, I would buy this car. (Since I do not have the money I cannot buy any new car). The action in type 2 is characterized by unreality.
If I were you, I would drive more carefully in the rain.
If dogs had wings, they would be able to fly.
Paula would be sad if Jan left.