The thing is the tranlation of "what for" and "why" have completely the same meaning in my native language. I'm interested in is there any difference between them in English.
That is, coudl you provide and example, if any, where these two constructions have the different meaning?
What for can either refer to a shortened "what (action) for" or "why" depending on the context.
I am going to the store.
(reply) What for?
In this sense it means "What are you going for?" if you were discussing groceries you might buy.
It could also mean "why" if the concern was why you were going to the store.
I am studying for the test.
(reply) What for? You will probably fail.
In this sense it means "why".
"What for" speaks to the purpose of something - what is the goal or objective and is essentially looking forward.
"Why" can also mean that, but also "Why" can speak to the cause and be an explanation of how something came to be - looking backwards in time.
In normal usage, "What for" is more rarely used - and tends to be quite specific. "Why" is more common, perhaps because it is more general and English always seems to love ambiguity :-)
