It is a latin phrase which means "We command."

Mandamus is an order or command from a superior court to a lower court or tribunal or public authority to perform an act, which falls within its duty and which it fails to do.

This is an order or command issued to secure the performance of public duties by the public authority and to enforce private rights withheld by such public authorities.

Such order or command of the court cannot be claimed as a matter of right. It is the discretionary power of a court to issue such writs.