Is there a difference between cystitis and pyelonephritis?

Kidney infection. Kidney infection (pyelonephritis) generally causes fever, chills and very significant flank pain. One generally feels "sick". Bladder infection (cystitis) rarely causes systemic symptoms. Discomfort in the pelvic area and irritative voiding symptoms are typical.
Bladder/Kidney. Cystitis is infection or inflammation of the urinary bladder. Pyelonephritis is infection of the kidneys.
Yes. Cystitis is a bladder infection. Pyelonephritis is a kidney infection. Cystitis usually presents with frequency, urgency and burning during urination. Also can have low abdominal pain and low grade fever. Pyelonephritis is usually associated with high fevers, flank pain and sometimes nausea and vomiting.