It is the vital part of the automatic sprinkler system that feeds fire fighting sprinklers, and these pumps work by feeding them with electricity, diesel or steam.
The pump suction line is usually connected to a fixed source of water (water tank, lake, …). The function of the pump is to deliver a high-pressure stream of water to the stalagmites connected to the water sprinklers and fire hoses.

Fire pumps are subject to NFPA code requirements