There are about 20 known varieties of the Cacao plant, but only three are commonly used in making Chocolate. There seems to be evidence that these are really categories containing a number of different sub-varieties but perhaps the sub varieties are just different locales.

1. Forastero ('foreign' in Spanish because it is the African cultivar) is most common -- 80% to 90% of all commercial Cacao comes from this plant. It has a high yield and is very resistant to disease. Not classified as "Fine Grade", this Cacao is used as a base to be blended with superior types of Cacao. Perfumed aroma with a fruity and bitter taste. The Amelonado form of Forastero is most often used. It is rather mild and in some cases can be unpleasant.
   
   
   
2. Crillo ('native' in Spanish, because it is the Venezuelan variety) is cultivated in small quantities in the original Cacao areas, especially in Venezuela. Traditionally the most rare and sought after of all the Cacao varieties, it produces "very fine" grade Chocolate sought after by some of the very high end Chocolatiers. Yields are low and the tree is fragile. Only 5% to 10% of the world's production is Crillo. It has more Theobromide than any other variety and therefore this is the variety that is sometimes suggested to contain caffeine. A small bit of it is sometimes mixed in to a large batch of the Forastero. The famous Ecuadoran Nacional is a form of Crillo. It is creamy and strong. Easily detectable sweet aroma, almost no bitterness, delicate taste.
   
   
   
3. Trinitero, which is grown almost exclusively in the Antilles, is a hybrid of the two other varieties and combines the best aspects of both. It accounts for 10% to 15% of world production. It has greater resistance to disease and damage than Crillo and many plantations that specialize in fine grade Cacao have been switching from Crillo to Trinitero. It produces generally excellent Cacao, being used more often in "very fine" grade Chocolate. Fruity aroma and slightly acid. It is spicy and sharp.
   
   Legend says that in the late 17th century a Spanish plantation of Crillo on the island of Trinidad, was destroyed by a hurricane. Assuming all the trees to be dead, it was replanted with Forastero; but spontaneous hybrids appeared, creating fortune out of the disaster.

If you taste the three varieties side by side, you will discover very distinct differences! I strongly prefer the Trinitero and am not very fond of the Crillo at all.