Ghee holds a peculiar place in the Ayurvedic kitchen: it is food, it is medicine, and it is the vehicle by which other medicines travel. Clarified butter, made by simmering butter until the water evaporates and the milk solids separate and are strained away, it keeps for a long time without refrigeration — a practical property that partly explains its prominence.
In classical terms ghee is described as increasing agni without aggravating Pitta, which is an unusual combination and the reason it appears so often. It is considered particularly suited to Vata and Pitta constitutions; Kapha types are advised to use it sparingly rather than avoid it.
Its role as anupana — a carrier — is the more interesting one. Ghee is lipophilic, and Ayurveda has long used it to carry herbs into the deeper tissues. This is what a ghrita is: a preparation in which herbs are cooked into ghee over many hours so that the medicine and the vehicle become one substance. Brahmi ghrita and Triphala ghrita are the two most people encounter.
In cooking, its high smoke point makes it more stable than most oils, and a teaspoon on warm rice or a chapati at the midday meal is the ordinary domestic use — taken at midday rather than at night, when digestive capacity is lower.
There is a widespread assumption that ghee should be avoided by anyone watching their cholesterol or their weight. That is a conversation to have with your own physician about your own numbers rather than one to settle from an article; the quantity and the context both matter.