Mother is an artificial intelligence (AI) network utilized by the United States Empire to manage various tasks.
Despite having no physical form, the artificial network named 'Mother' has a female voice presumably designed to set humans at ease. Her AI programming is quite intelligent, as she was able to answer questions from General Stone quickly and concisely regarding the identity of the Arm of Orion's leader Commander Soren.
Mother is used to manage tasks in both the United States Empire's military, the USIF, and the civilian sector. She is responsible for monitoring communications and intelligence in the United States Imperial Navy, and can even be used to transmit false intellgence to enemy forces, or intercept enemy communications, as she frequently did during the Outer Rim War. Mother is also responsible for monitoring the status of all Armored Infantry units and vehicles, as her voice is constantly projected through the communication set of every soldier wearing USIF Powered Assault Armor to notify friendly troops of changing battlefield developments or their personal status (armor and shield integrity, ammo capacity, whether requisitioned vehicles and deployables have been delivered, etc.).
In the civilian sector, Mother is known to be used for managing the largely automated Terraforming Towers, as her voice can be seen notifying personnel on the condition of each tower. Presumably, she also manages the automated Mining Lasers on planet Prometheus.