Carob (Ceratonia siliqua) is a legume and grows on an evergreen tree. It is also sometimes referred to as St. John's Bread since, as the story goes, St. John the Baptist subsisted on carob beans mixed with honey while he crossed the dessert. It was traditionally eaten in the Middle East as a source of sugar before sugar cane and beets were used for that purpose. The seeds are also referred to as "locust beans" and locust bean gum, a thickening agent, comes from these seeds.
Carob does not have the same taste/flavor as chocolate but many people like it. Per cup carob (compared to cocoa) has more calcium (36% vs. 11%), fiber (41g vs. 29g) and less fat (1g vs. 12g). Many people also prefer carob because, unlike chocolate, it does not contain the stimulants caffeine or theobromine and it is naturally sweeter than unsweetened chocolate.
Carob is rich in tannins creating a binding effect which can be helpful when given to someone with diarrhea. I have found documentation suggesting 15 g. of carob in applesauce (for flavor and ease of ingestion) is an acceptable dose for children.
Carob usually comes in a powder form (although it is possible to also buy it in blocks) and can be substituted for cocoa in a recipe, 1:1.5. -- if recipe calls for one cup of cocoa you would use one and one half cups of carob powder. To substitute for baking chocolate you can use 3 T. carob powder plus 2 T. water for one square baking chocolate. You can also purchase carob chips, look for the unsweetened ones,
I like carob and we do use it sometimes in baking. I don't consider it to be a "substitute" for chocolate, but instead another ingredient with it's own unique flavor. Give it a try, you may discover a new flavor to use.
photo courtesy of ca.wikipedia.org/wiki/Usuari:Chixoy