If it's not "real milk," then what is it?

The other day I bought a package of sliced mild cheddar cheese from Walmart (Great Value brand) and I noticed that, on the packaging, it says “made with real milk,” which got me wondering why is it that, lately, a lot of food products seem to have something similar on their labels…

Why do food manufacturers feel the need to stress that they’re using “real” ingredients? Does this mean that, in the past, they used “fake” ingredients? And as for the products that don’t have this on their packaging, what in the world do they use if it’s not the real thing? Should this be a matter of concern? Has this always been around and I’m just now noticing it, or is it just a marketing gimmick as it seems to be the case with a lot of other food descriptors these days?