Let's get one thing straight: This has nothing to do with corn. It is not called corned beef because the cows are fed on corn, neither is it called corned beef because corn is used as a filler in the recipe. In fact, the word corn refers to "corns" or grains of salt, originally used in the curing process. Modern corned beef is cured using brine rather than crystals.
In Britain, beef cured in brine is called salt beef, and this is finely minced and pressed to make corned beef. (In the US corned beef is what we call salt beef, and what we call corned beef may be known as bully beef.)
Corned beef is used as an ingredient in cooked dishes such as corned beef hash, or served cold with salad or in sandwiches.