The Mainland is on land in one of the UAE cities. You will have to have a physical office space for a Mainland business. On the Mainland, you can do business in the local market as well as outside the UAE without any restrictions.
In the UAE Free Zone, you can’t do business outside of its area. A Free Zone business can be run with or without a physical office.
In an Offshore company, entrepreneurs get full ownership of a company. A physical office is not allowed, and you can also do business outside of the emirates.