Urgent Care: Basically any issue a patient or their parent feels can't wait until they can get a doctor's appointment. ER: Patient/parent either feel this is an emergency or just that it can't wait for the pcp (see above). Also serves as a place to admit and stabilize those in true emergency situations. ICU: The place where the actual emergent patients go if not stable enough to be admitted to a regular floor. In a nutshell, that is. ICU is going to be your highest acuity. I believe ER definitely has its acute and fast paced moments each day. But in the little experience I have with that environment (few months of clinicals I did there in school plus being there as a patient)....a large percentage of ER patients are just "I have this illness and need an ABT script" or "my elbow feel funny" patients who don't have insurance and treat the ER as their pcp.