This is a question about the ghee making process, and also about the raw ingredients of ghee clarified butter.
Ghee manufacturers produce ghee from pure milk. Milk gets converted into curd, and by churning this curd, dairy butter gets prepared.
In the process of boiling, butter gets gradually free from moisture, and milk proteins like lactose and casein get eliminated.
Finally, the clarified fat of the boiled butter remains in the boiling pot, which ghee producers can collect by straining the oil by a strainer or by filtering with filter cloths.
The method of dairy butter boiling is a slow cooking process and this process creates lots of foam in the boiling pot.
Gradually the formation of foam (froth) gets reduced and ultimately froth formation gets stopped, which is an indication that ghee is almost cooked. Clarified butter looks yellow and it is produced in liquid form, and with a unique nutty aroma. When clarified butter is further boiled, it gets caramelized and ultimately the method produces pure ghee butter.
The question has two answers. First of all, ghee butter is made from pure cow milk, and secondly, ghee butter is produced by boiling dairy butter, and dairy butter is primarily produced from curd prepared from pure cow milk and by using churning process.