What's the difference between maximum security unit and the prison.

Maximum security is the grade of high security level used by prison systems in various states and counties.  In a maximum security prison or area, all prisoners have individual cells with sliding doors controlled from a secure remote control station. Often prisoners are confined in their cells 23 hours per day, but in some institutions, prisoners are allowed out of their cells for part of the day (recreation, education or medical). General population areas are limited with timed movements and escorts. Maximum security inmates often have long sentences and have a history of some violence that marks them as needed the heaviest supervision. When out of their cells, prisoners remain in the cell block or an exterior cage. Movement out of the cell block or pod is tightly restricted using restraints and escorts by correctional officers.