What does pain in the testicles mean?

Torsion, epididymitis. Sudden onset of severe testicular pain is torsion (twisted spermatic cord) until proven and an emergency. Slower onset of pain, often severe with scrotal inflammation could be epididymitis, which also needs to be checked out and treated with antibiotics. Other non emergency causes are varicocele, hernia, tumor or non-specific venous congestion.