Brig is a Navy Prison. The military doesn't have jails like the civilian jails. Military jails are there to hold individuals until they are either transferred to their unit or a military confinement facility, for pre-trial confinement, if they are military, or transferred to a cilivan law enforcement agency. Most of the time, people do not stay in a military jail for more than 8 hours.
A military confinement facility holds military members who have been convicted in a military courts-martial with confinement as a punishment, or those military members who are being held under pre-trial confinement, typically those who are a flight risk, or where the individual's safety or safety of others is present. Pre-trial confinement has to be approved by a military judge. Those in Pre-Trial confinement are separated from the other prisoners. They have zero interaction with the prisoners. When not preparing for their courts-martial, they can do many of the same things soldiers do. They are treated differently by the guards, namely, they are properly addressed by their rank, versus those in as punishment where the guards address these as Prisoner <Last Name>.
Former Army Legal NCO (JAG)