Common orange juice is made from the sweet orange. Different cultivars (for example, Valencia, Hamlin) have different properties, and a producer may mix cultivar juices to get the desired taste.
Orange juice wasn’t always the breakfast drink that it is today. In the mid 1910’s there was an overproduction of citrus fruits in California. Orchardists didn’t know what to do with the fruit and didn’t see another option but to destroy 30% of its trees. At that time, people didn’t have a fridge yet, so if they used the crop for juicing, the juice would only last for a day before it would start to rot. However, during this time, pasteurization was discovered and the national railway system was completed. Now, growers of the citrus could juice their oranges, pasteurize them for longer storage and then ship the juice to the big cities. This is how orange juice was first mass produced and mass marketed.