It is a technique from the yogic tradition to clean the intestines.
It takes about a whole day to perform the rather easy procedure and is followed by at least ten days of a strict diet.
Basically one drinks a lot of warm saline solution and does special movements in between the drinking to squeeze the water through the bowels.
One then proceeds to the bathroom and lets it out. Drinking alternates with the exercise and going to the bathroom until everything coming out on the backside is clear.
A kunjal follows, which is the cleaning of the stomach with saline solution. A neti is also done, the cleaning of the nose with saltwater.
If one has gallbladder problems an additional procedure is performed which gets rid of them completely.
It is very important to rest afterwards and eat a special meal which is easily digested. Usually thats daal with rice and ghee.
It will take some time until the intestinal flora grows back which means the digestive system cant digest heavy foods. Indeed one could even die from eating a very hot pepper for example. So follow the diet.
Best to perform with someone that knows the procedure the first time you do it.