Here are some possible interpretations:
* "Just you and nothing else" - This is the most common interpretation. It suggests that the speaker only wants the person they're talking to, and nothing else.
* "Nothing else matters but you" - This implies that the person is the most important thing in the speaker's life.
* "You are the only one who matters" - This emphasizes the speaker's focus on the person.
* "You are my everything" - This is a more romantic interpretation that suggests the person is everything to the speaker.
Ultimately, the meaning of "nada y tú" will depend on the specific situation and the tone of voice used.