What is the meaning of Mains?

plural of main

The domestic electrical power supply, especially as connected to a network or grid.

A large-scale network or grid supplying any of various other services, such as water, gas or sewerage, to properties.

The main course of a meal.

third-person singular simple present indicative of main

The farm attached to a mansion house.

plural of main

minus sign

Source: wiktionary.org