Literally, that is the meaning of "Tacos de Canasta" - the lowest common denominator of street food in Mexico.
Starting from 5 pesos each (roughly 50 US cents, in 2011) - they are assembled from ingredients stored in a wicker basket: minced meat, beans, potatoes, chicken, etc.
And mind you, Mexico has some of the best street food in the world, but "Tacos de Canasta" are
outright dangerous. The hygiene of the whole set-up is very poor, and a foreigner is bound to get some serious gastro disease after having one of these.