What does severe tendonopathy of the distal aspect of the supraspinatus tendon mean?

The supraspinatus tendon runs from the muscle on the outside of the shoulder blade, over the shoulder joint and inserts on the humerus. The distal aspect is the part that inserts onto the humerus. Tendonopathy is unclassified disease of the tendon; this could be due to infection, trauma, degeneration or neoplasia.

In practical terms, this is one of the tendons associated with the rotator cuff. It is severely damaged and may be close to the point of spontaneous rupture. Surgery is not a fun option as it is painful, recovery is time-consuming and 100% function is not likely to be restored. I suspect your doctor would have recommended strict rest to let the tendon heal itself - no lifting weights, no raising the arm over your head, possibly wear a sling.