Capete is both a form of cap ("head") and of capăt ("extremity", "end"). To make matters even worse, cap has actually 3 separate entries in the dictionary, each with their own meaning and declension table.
In this sentence, though, capete is the plural of cap in the sense of "head", for which I provided a link to the right entry in the dictionary.
It's the “not” (negation). In English, only auxiliary verbs (to do, to be, etc) can be negated directly (I do not…, I am not…), for other verbs you need to add “to do” when you negate them (It has… → It does not have).
The same applies when building a question.
Maybe there is a more detailed explanation in one of Duolingo's English courses. Try looking for “negation.”