GRAMMAR: CONDITIONAL SENTENCES

A conditional sentence is form by two different parts: If-clause and main clause.
The order of the parts does not matter, but we should remember that if we're going to put the if-clause first, it must be followed by a comma.

I will buy new clothes if a have money tomorrow.
If i have money tomorrow, I will buy new clothes. 

There's four different types of conditional sentences, and each one of them uses a different tense. 

ZERO CONDITIONAL: If/when + present + present.
For example; The movie stops if you press that button. 

FIRST CONDITIONAL: If/unless + present + future.
For example; If I clean the house, my dad will be happy. 

SECOND CONDITIONAL: If + past + would + inf. 
For example; If I studied, I would pass. 

THIRD CONDITIONAL: If + past perfect + would have + present perfect.
For example; If I had lost my mobile phone, I would have been punished.