Jathara Parivartanasana (sometimes written Jathara Parivartan Asana) is a yogic exercise that also carries names like Revolved Abdomen Pose, Waist Rotating Pose, Belly Twist, Abdominal Twist, Torso Twist, or Spinal Twist.
Jathara is the Indian Sanskrit word for stomach, belly, or abdomen, although it may also have some other meanings such as womb, cavity, interior, or bosom.
Parivartan is likewise a Sanskrit word that means moving to and fro, turning about, rolling about, turning round, revolving, whirling round, or inverting, and Asana means posture or pose.
At any rate, Jathara Parivartanasana is performed reclining on the back (supine position) with the arms spread touching the ground on the level of the shoulders (one could say the arms spread like the Lord Jesus on the cross). You can see an example in the lead image of this post.
The knees are then raised up in the direction of the chest and then lowered to one side, while keeping the opposite shoulder as much as possible on the ground.
This is repeated as a side-to-side roll by bringing the knees to the other side, and so on, which could be done as a continuous movement or rather after a pause in each position.
Another variation is to keep the legs straight lowered to one side, which can be done by first raising the knees to the chest and when in lowered position to one side subsequently straightening the legs.
In addition, the exercise can be done by simultaneously contracting and subsequently relaxing the pelvic floor muscles while getting into the pose.
Usually no special breathing pattern is used, but just normal, relaxed breathing. Nevertheless, typically one would perform slow and deep Abdominal Breathing and inhale while starting a turn, and exhale when reaching the ground.
The health benefits of this yogic exercise are thought to include deep relaxation, improvement of blood and lymph circulation in the abdominal region, relief of lower back pains by stretching the low back muscles, general relief of stiffness and tightness, and strengthening and toning of the abdominal muscles and internal organs through the repetitive massage movements induced by moving the legs alternately from one to the other side.