Arrabales refers to the poor suburbs, slums, or the outskirts of a city. It's a word loaded with social and cultural meaning that you won't find in a typical textbook.
In this song's story, the taxi driver uses it to draw a stark contrast between his life and that of his rich passenger. He tells her, "Usted sufre en su mansión, yo sufro en los arrabales" (You suffer in your mansion, I suffer in the slums), powerfully highlighting the theme that heartbreak and suffering exist across all social classes.
This song is a whole movie packed into five minutes! Ricardo Arjona tells a story from the perspective of a taxi driver working a slow night in his old VW. He picks up a beautiful, crying woman named Norma. She's upset because her rich boyfriend is cheating on her. The driver, trying to be a hero, offers his help: "Cuente con un servidor, si lo que quiere es vengarse" (Count on me, if what you want is revenge). Of course, one thing leads to another, and they end up at her place for what he describes as kissing "hasta la sombra" (even her shadow).
They bond over their shared unhappiness. He complains about his own marriage, saying "Mi mujer y mi horario han abierto un abismo" (My wife and my schedule have opened an abyss). To get back at her man, Norma takes the driver to the bar where the cheating is happening. They walk in and see her boyfriend with another woman. And in a perfect soap opera twist, the driver realizes the other woman "Era mi mujer" (It was my wife). The song ends with the crazy revelation that their respective partners continue the affair, and Norma now calls the taxi every night at 10 PM, continuing her own affair with the driver. It's a wild story of revenge, coincidence, and two wrongs definitely not making a right.