What exacly is a shunt for dialysis?

Fistula: It is a sort of connection between artery and vein either using own blood vessels or with synthetic graft. This site is the access for hemodialysis.

Your blood access: A "shunt" or "fistula" is the way the blood is removed from your body, and returned to it. It can be a fistula, graft, peritoneal catheter, or hemodialysis catheter. Simply put, you need something to get the waste products out of your blood. In hemodialysis, the machine acts as your kidneys and the shunt is used to take the blood out and return it from either tubes (catheter) or needles (shunt).