The structure indicated is the cephalic vein.
The cephalic and basilic veins are the main superficial veins of the upper limb. The cephalic vein originates from the dorsal venous network of the hand and drains into the axillary vein by passing through the deltoid and pectoralis major muscles.
In the cubital fossa, which is the area located anterior to the elbow joint, the cephalic vein is joined to the basilic vein via the median cubital vein.
In the clinical setting, the median cubital vein is a convenient and common location for obtaining venous access for the administration of fluids or intravenous medication.
Learn more about the veins of the body in this tutorial.