What is the difference between common cystitis or urinary tract infection and interstitial cystitis or painful bladder syndrome?

Common cystitis or urinary tract infection is usually caused by bacteria and responds to antibiotic treatment.
Interstitial cystitis or painful bladder syndrome is not caused by an infection. It is a chronic, autoimmune disease characterized by pelvic pain associated with bladder filling that is relieved by urination and is often associated with persistent urinary urgency and frequency.