Commands in Spanish are part of what we call the imperative mood. In this way, tú (that means you) is the subject pronoun that matches the second person singular and is given in informal form. You use it when talking to your friend, your cousin, and other person that is familiar to you. So the correct tú command in this case is come and it comes from the verb comer that means to eat: So the sentence:
<em>Come la manzana </em><em>means </em><em>eat the apple</em>
