Mate is the name of a typical beverage of the river plate zone, shared with south of brazil and argentinians. It's an infusion of a weed named "yerba" (wich actually in spanish means weed), like tea, but the weird thing is that it is drinked (sipped actually) in a special recipients made out of a dried, hollow "fruit" (it's kinda small pumpking) called mate, wich names the whole thing. You sip it with a metal thing called "bombilla". There I've said it. It's like coffe, some sort of stimulator, very popular among students to start the day, and to stay awake until late.
Half of the population or more are on it, people carry their own "mates" to work, and it's also a social drink, it's unpolite to have mate and not offer, and if someone requests "a mate", while you are having it's almost illegal to deny it.