"When, where and what will be eaten?"
Translation:Wann, wo und was wird gegessen?
The first "werden" ("wird") is auxiliary for future tense, the second one is auxiliary for passive voice. My best explanation for how to know which one is for future tense and which one is for passive voice is the word order. The "future-werden" is put previous to "gegessen" (I don't know how this verb form is called gramatically), the "passive-werden" after it. If you say "Was wird gegessen?" ("What is being eaten?"), the "wird" is auxiliary for passive.
The English sentence is technically nonsensical, as you can't say "When will be eaten" or "Where will be eaten" but I suspect most people wouldn't give it a second thought if they heard it, just interesting that German seems to function the same way. A pedant would insist on "When and where will what be eaten?"