A microsystem is a system that is designed for use by 1 person. It generally is small enough to sit on a countertop, or be enclosed within a single bookshelf.
A minisystem is a system that is designed for use by 2-3 people. It generally is contained within an enclosure that can be easily moved, either by the use of wheels on the bottom of the frame or as a single unit by forklift.
A standard system is a one that is designed for use by 4-6 people. It will have multiple grow beds and is usually housed within an enclosed structure such as a greenhouse.
A commercial system is a system that is designed to produce output for hundreds to thousands of people, and is generally constructed by those interested in pursuing aquaponics as a revenue-generating venue.