An outpatient for that matter is treated in the hospital as a patient that has visited the hospital for consultation. On the other hand an inpatient is treated in the hospital only after admission. This is one of the main differences between outpatient and inpatient. An inpatient gets admission into the hospital upon his arrival at the premises of the hospital. He would spend a certain period of time in the hospital and is given a room to stay in the premises. He is attended to regularly by the doctors that are appointed by the hospital.
http://www.differencebetween.com/difference-between-outpatient-and-vs-inpatient/
Observation services are hospital outpatient services you get while your doctor decides whether to admit you as an inpatient or discharge you. You can get observation services in the emergency department or another area of the hospital.
https://www.medicare.gov/what-medicare-covers/part-a/inpatient-or-outpatient.html
1 You're an outpatient if you're getting emergency department services, observation services, outpatient surgery, lab tests, or X-rays, or any other hospital services, and the doctor hasn't written an order to admit you to a hospital as an inpatient.
https://www.medicare.gov/what-medicare-covers/part-a/inpatient-or-outpatient.html
Outpatient surgery, also known as ambulatory surgery, same-day surgery, day case, or day surgery, is surgery that does not require an overnight hospital stay. The term “ outpatient ” arises from the fact that surgery patients may go home and do not need an overnight hospital bed. The purpose of outpatient surgery is to keep hospital costs down, as well as saving the patient time that would otherwise be wasted in the hospital. Outpatient surgery has grown in popularity due to the rise in outpatient surgery centers and improved technology.
https://en.wikipedia.org/wiki/Outpatient_surgery
1 The day before you're discharged is your last inpatient day. 2  You're an outpatient if you're getting emergency department services, observation services, outpatient surgery, lab tests, or X-rays, or any other hospital services, and the doctor hasn't written an order to admit you to a hospital as an inpatient.
https://www.medicare.gov/what-medicare-covers/part-a/inpatient-or-outpatient.html
Your doctor services. You come to the ED with chest pain, and the hospital keeps you for 2 nights. One night is spent in observation and the doctor writes an order for inpatient admission on the second day. Outpatient until you’re formally admitted as an inpatient based on your doctor’s order.
https://www.medicare.gov/what-medicare-covers/part-a/inpatient-or-outpatient.html
An inpatient gets discharged once he is cured of his ailment or disease. On the other hand an outpatient does not experience the event of getting discharged since he or she never gets admitted in the hospital for treatment.
http://www.differencebetween.com/difference-between-outpatient-and-vs-inpatient/
Complications related to surgery occur less than 1% of the time in outpatient settings. However, in terms of patient safety, non-hospital settings are not as regulated as hospitals are.
https://en.wikipedia.org/wiki/Outpatient_surgery
On the other hand an outpatient leaves the premises of the hospital after consulting a doctor that visits the hospital or that is appointed by the hospital. Unlike the inpatient he does not spend a certain period of time (days) in the hospital.
http://www.differencebetween.com/difference-between-outpatient-and-vs-inpatient/
Your hospital status—whether you're an inpatient or an outpatient—affects how much you pay for hospital services (like X-rays, drugs, and lab tests) and may also affect whether Medicare will cover care you get in a skilled nursing facility (SNF) following your hospital stay.
https://www.medicare.gov/what-medicare-covers/part-a/inpatient-or-outpatient.html
what is the outpatient at the hospital
The outpatient is a patient who treated in the hospital as a patient that has visited the hospital for consultation.