This was the route taken by pilgrims from southern Spain once the reconquest of Seville had taken place and led north, in more or less a straight line, via Seville, Zafra, Merida, Caceres, Salamanca and Zamora. After that there were (and still are) several variant routes, one of which, described here because it is the waymarked one, it joined the Camino frances in Astorga. Others went through Verin and Ourense and straight from there to Santiago or joined up with one of the Portuguese routes through Braganza
The Via de la Plata is reliably waymarked with yellow arrows from the outskirts of Seville to Astorga and is easy to follow.
At present, however, not many people take it, presumably because it is not yet very well known