To be daydreaming or absent-minded, not paying attention to what is happening around you. The literal translation is 'to be on the moon of Paita', Paita being a city in Peru.
Examples
- Spanish: Juanito, deja de estar en la luna de Paita y concéntrate en tu tarea.
- English: Juanito, stop being on the moon of Paita and concentrate on your homework.