What is Achilles tendon rupture like?

Awful. A full blown true rupture leaving a depression in the tendon called a dell may require surgery. An MRI will help make that decision. A partial rupture or tear may not. The latter will need immobilization, non weight bearing, rest, elevation, ice, and meds...
Not fun. Achilles is a major tendon in the leg which plays important role in foot function. Ruptures are sometimes treated via cast immobilization and other times primary repair via surgery. Rehab can be couple of months.