Karo is a brand name for corn syrup.  Back in the good ol’ days, well, in the old, old days, people got their corn syrup at the store from a barrel.  The first company to put the syrup in a small bottle or individual purchase was the Corn Products Refining Co. of New York and Chicago, and they called it Karo, so “Karo” became the word we all associate with corn syrup, just like we associate “Kleenex” with tissue.

Corn syrup is mainly glucose suspended in water.

High-Fructose Corn Syrup came on the scene in 1957.  It gets its higher fructose amount by adding enzymes to regular corn syrup.

High-Fructose Corn Syrup is composed of  35% glucose, and 65% fructose, and although the name implies otherwise, the sugars come not only from corn, but can also be from fruits and/or honey. Since fructose is sweeter than glucose, it is a sweeter syrup.  It is much sweeter than regular corn syrup, and therefore is used by manufacturers a lot because they can use less, and cut costs.