A colectivo is a form of transportation in Mexico that is generally geared towards moving the population around Mexico's vast labyrinth of roads and highways. Quite often the colectivo is a mini-van.
In tourist zones such as the Mayan Riviera the colectivos are new vans with air-conditioning. Get out of the tourist zones and some of the vans are pretty reggae-muffin.
In some places they are called "combis". In the Chiapas on many roads in Zapatista territory the colectivoes are blue pick-up trucks with a tarp on the back. The "old-style" colectivos are still in use in Chiapas, Campeche and Chetumal but not in the Mayan Riviera.