Tulsi is an herb with the biological name "Ocimum tenuiflorum." It is commonly known as "Holy Basil." It belongs to the same family of herbs that are known as basil and different varieties of which are extensively used around the world in cooking.
Tulsi has a very important role in the Hindu religion and in the form of medicine known as Ayurveda. You would usually find this planted in the garden of most Hindus if you were to visit India. The plant is considered sacred and usually worshipped every morning. The leaves of the plant are used extensively in religious ceremonies, particularly as the ingredient of a drink that people drink after the prayers are done.
Tulsi is proven to have many health benefits, some of which make it useful in curing common colds, stomach disorders, poisoning and malaria. It is also used for cosmetic purposes and applied as a cream.