All I know about Was für ein is that it is a type of pronoun (but I don't know what type exactly it is). I also don't know how it translates into English.
Was für ein...
is a phrasal expression which can be used in a question to ask "what kind of". For instance:
"Ich möchte Tee bestellen"
"Was für einen Tee möchten Sie?"
This translates into:
"I would like some tea, please"
"What kind of tea would you like?
You can also add a verb inside it (so that it is split up), like in:
"Was willst du für einen Tee?" --> "What kind of tea do you want?"
Please note that you need to change "ein" into "einen" because the subject is "du" and you are asking information about an object (accusative).
Another usage is in affirmative sentences where is basically means "what a...".
Was für ein Tag! ---> What a day!
In this case the speaker expresses the simple fact that he/she has had a peculiar day (in a bad or in a good sense).
A vocabulary reference is here: