To live off the grid is to have a self-sufficient lifestyle that doesn’t rely on public utilities like electricity, water, or gas.
A power grid is a network that delivers electricity to homes and businesses, so being off the grid means living disconnected from that system. The term also applies to being disconnected from other public utilities, like water or gas. People who choose this lifestyle often rely on solar panels for power, wells for water, and gardens to grow their own food.