OR/Circulating nurse is in charge of everything that happens in the operating room. He/she gets sterile supplies for scrub nurse/tech, gets patient prepped (betadine scrub, positioning on the table), documents everything and makes sure the anesthesiologist has his supplies. PACU - once the patient is done with surgery, he is wheeled off to a PACU area (sometimes the patients room like after a c-section) and is watched one-on-one by the PACU nurse. The PACU nurse is taking vital signs every 15 minutes until the patient is stable. Nausea and vomiting are very common after surgery so they make sure the patient does not aspirate. They have suction ready and other emergency supplies just in case. Not sure about perioperative. There is a pre-operative nurse that does the vital signs and assessments before surgery. She will reconcile medication that the patient is taking at home, get a thorough history of prior surgeries and anything that might affect the surgery or recovery, allergies. If the patient needs prophylactic antibiotics, they are the ones to set this up.
I have watched surgeries in the regular OR and obstetrics OR and the regular OR splits up these nursing jobs into 3 different entities. In obstetrics, one nurse traveled with the patient, setting up the IV, getting a history. Then she became the circulating nurse in the OR, getting all the supplies and documenting everything. Then she followed the patient to her postpartum room, where she took vital signs Q 15 min for an hour.
If you have a test coming up, try visualizing what you think each of these jobs entail.