Panchgavya is the mixture of 5 things from cow in a certain proportion - her milk, yogurt, Ghee, urine, and dung.
Chhaandogya Upanishad (1.10) says that,
Gavyam su-madhuram kinchiddoshaghnam krimi kushtanuth |
Kandoom cha shamayet pittam samyagdoshodare hitam ||    (go-mootra is a little sweet, it is anti-infection, it cures leprosy).

Panchagavya is said to be a potent medicine. There are Mantra for adding each ingredient and making the Panchgavya.
The proportion of the mixture is
(1) cow's urine 100 gms (one palam),
(2) cow dung of the size of a medium thumb
(3) cow's yogurt 300 gms 
(4) cow's milk 700 gms
(5) cow's ghee 100 gms 
and 100 gms of Darbhaa grass Jal.

This mixture is called Panchagavya because it contains five ingredients derived from the cow.

Varun resides in the urine of the cow. Agni resides in the cow dung. Vaayu resides in the yogurt. The Moon resides in the cow's milk, The Sun resides in the cow's ghee. Women who have the impurity after delivery should take panchagavyam to become free of it. If it is taken for 41 days continuously even a patient of epilepsy will be relieved of that ailment.