While related to the more well-known Ocimum basilicum, the basil used in cooking, Holy Basil is a medicinal herb used to make teas and extracts. It's known as a sacred plant in India.
The Rama and Krishna varieties share the interchangeable botanical names Ocimum tenuiflorum and Ocimum sanctum; the two Latin names are synonymous with each other. They are, however, more like fraternal twins: The Rama variety is a short, annual, heavily flowered plant originally introduced to the U.S. as "Holy Basil". It is the most common type found in cultivation in the U.S. and is known for its cooling and mellow flavor and makes a delicious tea.
Vana has its own Latin name: Ocimum gratissimum. It is the original wild bush basil. Its natural habitat ranges throughout India and across North Africa and down into East Africa. Of the three varieties, it is the most fragrant.
Holy Basil Leaf, Rama & Krishna (Ocimum tenuiflorum/Ocimum sanctum): Holy Basil may modify glucose regulation.
Holy Basil Leaf, Vana (Ocimum gratissimum): Not to be used during pregnancy.