"What do you want to eat?"
Translation:Co chcesz zjeść?
"dok." is "dokonany" = "perfective". "niedok." is "niedokonany" = "imperfective".
The Polish names of those aspects could be better translated as "accomplished"/"not accomplished". Until some point in the course (this exact skill), you only learn imperfective verbs. They focus on the process. They mean that something was either not finished, or the result is unknown/unimportant.
Perfective verbs focus on the result. They cannot be used in the Present Tense, because finishing doing something happens at a specific moment, it's not a process, it cannot be continuous.
The problem is, that often both versions are correct translations of English, one is usually more probable, but the other can also work.
"zjeść" focuses on the result. The meal is supposed to be finished, the result is supposed to be finishing a meal and hopefully not being hungry anymore. "jeść" focuses on the process, so it's more like "What would you like to be eating", only that the Polish version is natural. It works quite fine in this sentence, actually.