Orujo is a liquor distilled from grapeskins at the annual harvest. It is best known to pilgrims as orujo de hierbas, with herbs and honey-- very potent, but very agreeable. It is lovely after a meal.
Orujo blanco is the pure liquid, but seems to have an anise flavour, much like grappa or the better ouzos. Casero means that it is home-made, as Spanish farmers are allowed to distill a certain amount (I heard 100 litres) for home use and walking through Galicia and Asturias, I would see shop windows with distilling equipment for sale. They will often trade orujo for meals, or sell it under the counter to bars and restaurants. I find that it is purer and subtler than commercial orujo, but I would counsel pilgrims to make sure that they do not have to walk too far afterward. A Californian friend kindly bought me a bottle (thank you, Grant) and when he asked the farmer's wife what the proof might be, she just laughed at him: "who knows? who cares?"
Pilgrims will sometimes notice that there are vinegar shakers placed near the coffee machines.... they are not vinegar shakers at all, but they do contain orujo blanco. Upon enquiry, I was told that it was only to flavour one's cafe solo, and that this was especially appreciated by those whose doctors forbade them to use sugar. Orujo blanco can usually be purchased from village bars, but is usually sold in corked wine bottles and even sometimes in old coca-cola bottles. It is always excellent.
It also comes as orujo de cafe, made with coffee beans, but I think that this is a horrible drink, and so will ignore it.