Translation:Are you buying a fridge for the kitchen?
Ah... the old 'por' vs 'para'. Still gets me on occasion. In this case the kitchen is the recipient of the refrigerator. Whenever there is a recipient involved the word 'para' is used. Hopefully the following will help you as it did me:
Think of 'para' as a straight arrow imparting a direction of sorts with a final destination. Use 'para' for Deadlines, Destinations, Goals, and Recipients. In fact if you are in doubt which to use in a conversation... use 'para'. Most of the time it will be right.
Now 'por' is a little trickier. Think of it as a squiggly line or an X. It imparts and 'exchange' or 'motivation' of sorts without the clear ending or destination that 'para' had. Use 'por' for Communication, Duration, Exchanges, Motivation, and Travel.
'Estas comprando' is present progressive tense which is used when the action is currently happening while the speaker is talking.
'Tú compras' is simple present tense which only means that the action happened now but is not necessarily occurring at this very moment.
In this sentence, the verb comprar is conjugated in the present tense, "compras", which can mean either "Do you buy a fridge for the kitchen?" or "Are you buying a fridge for the kitchen?". If you wanted to say, "Did you buy a fridge for the kitchen?" you would need to use the past tense of comprar, compraste: "¿Tú compraste una nevera para la cocina?"