Whats the difference between a critical care and an intensive care unit?

Same thing: Different hospitals have different terms for specialized care units that take care of the sickest patients.

Interchangeable: The terms are essentially interchangeable. Critical care and intensive care are both used to describe a unit or medical specialty in which seriously ill or injured people receive care. These units may be general critical care or intensive care units that care for a wide variety of conditions, or neonatal, pediatric, adult, cardiac, surgical. Or neurosugical units.

They are the same: An intensive care unit is the same as a critical care unit. Different hospitals call it different things.