Campesino means simple farmer\ in Spanish. While English has a possible equivalent, peasant, this word has negative connotations that the Spanish word doesn't have. This is because in the Hispanic world, many people, referred to as campesinos, still survive from subsistence farming, whereas subsistence farming died out in the white anglophone world at least a century ago. Hence, it is customary in English to refer to subsistent farmers in Central or South America as campesinos.
El Campesino was a military leader of the Second Spanish Republic during the Spanish Civil War.