Power inverters give us high voltage AC from low voltage DC. They're great. They also waste a little power just by being on, even if nothing is plugged in.
If you are working with a small battery system, you may have gotten in the habit of turning this device on only when you need it.
This circuit disconnects the battery from the inverter with an external switch. This way, you don't have to splurge on an inverter with a remote just to hide it away. Breaker sizes and wiring terminations are just examples. Sorry this is my best handwriting.