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1. 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.
2. 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.
3. Third Conditional (Type III) :The third conditional (also called conditional type 3) is a structure used for talking about unreal situations in the past. In other words, it is used to talk about things which DID NOT HAPPEN in the past. Type 3: if + past perfect + perfect conditional
Full form : If I had studied harder, I probably would have passed the exam. Contracted form :If I`d studied harder, I probably would`ve passed the exam.
Example: If I had had the money, I would have bought this Audi. (But I did not have it, and so did not buy). If you had driven more carefully, you would not have had an accident. (You had an accident because you didn`t drive carefully enough.) If we had played a little better, we could have won the game.(We didn`t play well, so we lost the game.) The action in type 3 is characterized by impossibility.
While type 1 and type 2 focus on the present or future, the time in type 3 is the past and signifies a completed action in the past. The condition, therefore, cannot be fulfilled because the action in the if-clause did not happen.
Summary
IF-CLAUSE
RESULT CLAUSE
Explanation

simple present verb
simple present verb
if-clause uses simple present result clause uses simple present

If it rains, If it gets cold enough, If I don`t do my homework,
my car window leaks. water becomes ice. I learn nothing.
<-expresses an established or predictable fact, it expresses a general truth

If Marie doesn`t eat dinner, If I exercise,
she gets hungry at midnight. I look great!
<-expresses a habitual situation or activity.

If someone calls,
take a message please.
<-gives a command

simple present verb
modal + simple present verb
if-clause uses simple present result clause uses modal + verb

If it rains,
my window might leak.
<-expresses a fact 

If the phone rings,
I will answer it.
<-expresses a future situation

If the weather is sunny,
we can go to the beach Sunday.
<-expresses a future activity