El Guagua is another way to say "Autobus" o "Camioneta" in Spanish. It's a fixture of many Latin American cities. Many of these buses come from retired American school buses. This photo was taken in Antigua, Guatemala and shows off the creativity and resourcefulness of these entrepreneurs.
If you want to learn more, watch this documentary. It's available on Netflix.
La Camioneta: The Journey of One American School Bus.