The most common form of this expression is “밥 먹었어요?” To review when to use each form above, see my lesson on politeness levels.
먹었어 is the past tense conjugation of the verb 먹다, meaning “to eat.” Need a refresher? See my lesson on past tense conjugation.
You can add the object marker “을” to 밥, like I did in the formal example above, but in conversation this is often omitted. See my lesson on the object marker for a refresher.
In Korean, 밥 literally means rice, but it also translates to food in general.