Patient gowns are what is worn when you stay overnight at a hospital as a patient.

A disposable isolation gown or suit is intended to protect a medical provider from exposure to blood, bodily fluids or other infectious material as well as protect the patient from being infected. The Isolation suit (vs gown) is often called coveralls as they look like coveralls and typically zip up the front and may or may not contain a hood or foot coverings. 

A Surgical gown is typically used as a two way protection device during an operation. Not only does it protect the provider and patient in the same ways as an isolation gown, it also can block things from attaching to skin or clothing during surgery, such as bacteria. For example, these are typical in a strict sterile environment where you are doing an invasive surgery to protect the patient and the surgeon from possible contamination that could cause a bacterial type infection.

There are 4 levels of Isolation and Surgical Gowns, the most common usage during Covid for testing, vaccines, caring for patients is the Level 1 or Level 2. There are a few standards of the levels, here is one example of the AAMI standard for levels.

Level 1 offers minimal water resistance ( = 4.5 g)
Level 2 offers low water resistance ( = 1.0 g)
Level 3 offers moderate water resistance ( = 20 cm)
Level 4 offers Blood and viral penetration resistance (no penetration)