The Mexican cactus paddles commonly used in salads and tacos are called nopales. The word refers to the edible pads of Opuntia, the cactus group also known in English as prickly pear or tender cactus.
Nopales are harvested as young, tender pads, then cleaned of their spines and sliced or diced. They can be eaten raw, grilled, boiled, or sautéed. Their flavor is mild and slightly tart, often compared with green beans, while their texture can be crisp and mucilaginous because the pads contain a naturally gel-like liquid.
In Mexican cooking, nopales appear in tacos, salads with tomato, onion, and panela cheese, huevos con nopales, and carne con nopales. The fruit of the same cactus is different: it is called tuna in Spanish and prickly pear in English. Another common mix-up is agave or maguey. Those are different plant groups; although their leaves and stems are also important in Mexican food and drink traditions, they are not the cactus pads called nopales. Mexico has about 114 known Opuntia species.