There are no specific characteristic for an Auxiliary pump.
Let me describe a situation for one to understand. In a refinery or a chemical plant It is mandatory to have fire control system
One usually has buried underground large diameter pump system with a large reservoir of water and hopefully a near exhaustible supply of raw water.
This system is always kept under pressure to make sure the availability of plenty of water to put out a fire. This is done by a Jacking pump/auxiliary pump and if any of the fire posts are opened the water will come with a high force and a power drops in the system the main pump will start and maintain the pressure and water. Certain times we have many pumps as drawals increase then we designate others as auxiliary pumps’
Let me go to another Scenario. Sometimes we have very large Hydraulically operated valves that are opened by powerful Hydraulic actuators. They in turn requires require small hydraulic system to open /close the valve. you may call them auxiliary motor.
As the term motors Auxiliary means that which starts the main action. It can be Electrical/hydraulic/Compressed air/ Vacuum or even Transducer.