Korean language: 뭐 드시겠어요? In my text book says "What will you eat?" But surely this means "what do you want to eat?"
If we break down
뭐 = what
드시다 = to eat (honorific form)
겠 = future particle
어요 = polite ending
So the most literal translation is, as your book says, "what will you eat?" or "what are you going to eat?".
Of course you are right that this particular phrase in Korean might be said in a situation where in English, we might more naturally ask "what do you want to eat?" - but then it might be even more natural to, e.g. in a restaurant, ask "what would you like, sir?", which is a further departure from the literal meanings of the words in the original Korean.
It comes down to a fundamental problem with translation, especially when it comes to languages that work very differently: You can't just change the words to the equivalent words; you have to look at the intent of the original language, and then find words in the target language that express that intent.
먹다 in its honorific form is
잡수시다 but also can be
드시다. So in short,
무엇을 드시겠어요? then is the honoring way to say
I see your question has changed. If you are now asking about why the text book is using the future tense
will it is because the verb conjugate
겠다 is a future tense. Then therefore while splitting semantic hairs, the future tense version of "Dude what do you want to eat?" must be "Dude what are you going to eat?". Additionally, the phrase
무엇을 드시겠어요? does not include the feeling/meaning of
want in any of the words. For "What do you want to eat?" you might try:
뭐 드시고 싶은 것이 있으세요?
Which probably more literally translates to "Is there something that you want to eat?"