what does it mean when the box of orange juice reads..."from concentrate"?

Answer 1

It refers to the way it was processed. After getting the juice from the oranges, the manufacturer then removes the liquid and thus you are left with the "concentrate". This is probably done for cost efficiency when shipping the product from its origin.

At a later time, another process is used to add water back to the concentrate, thus making juice again. You could simulate this by buying frozen, concentrated orange juice and then following the directions to add water. Essentially, you're doing the same thing.

Answer 2

It means that orange juice - produced in for instance Brazil - is concentrated (thickened by letting water evaporate). Concentrate is much less bulky and easier and cheaper to transport from Brazil to the factory - in for instance the U.S. - where water is added again to get a normal strength orange juice.
Unfortunately some of the aromatic components of the juice are lost and that is why fresh orange juice tastes so much better.

Answer 3

water is added to the carton. from concentrate juices are not as rich and flavorful as 100% pure juices that are NOT from concentrate. concentrated juices tend to be more sour tasting and not as sweet as the pure juices.