Non-alcoholic beer is beer that has been brewed, and reheated, and boiled after it is ready for bottling. This burns out the alcohol. It is then injected with inert gas, and bottled. Although NAs are starting to gain popularity now, they date back to the Egyptians. This is what they offered to the gods.
Light beers are simular to NAs in that they are watered down, to reduce the alcohol.
Taste is not that great with light beers, because of this. Sometimes fizz is added to these beers to make them look good. They should be served icy cold in that they are thirst quenchers, rather than a connoisseur's search. A friend into NAs claim that the German NAs are the best. The biggest fiasco of NA beers was the attempt of Anheuser-Bush back in 1978.