Chakra is a Sanskrit word that translates to wheel or disc. It refers to the seven main energy wheels or centers within the body. They run up the center of the body aligned with the spine, starting from the base extending out to the crown of your head.
Lord Vishnu is the Preserver or Sustainer of life with his steadfast principles of order, righteousness & truth. When these values are under threat, Vishnu emerges out of his transcendence to restore peace and order on earth.