lol can I put it in language I can understand lol? It sounds like even if I turn off the circuit breaker for that box, other wires in that box COULD be associated with ANOTHER circuit breaker, and if that second circuit breaker is on, I could have a problem?
I guess to be REALLY safe, I should turn off the MAIN circuit braker? Thanks.
That is *exactly* the problem with SHARED neutral and ground returns, most common in older houses that have had the wiring and sockets changed here and there over the years. Ideally, each breaker's branch circuits have their own isolated neutral and ground returns not connected in any way to another circuit's returns. When neutrals and grounds are shared between switched-off and live circuits, and you undo a bundle of neutrals or grounds in a wire nut, then *some* of those neutrals and/or grounds dangling loose are still connected to ground at the breaker box and *some* are connected to live circuits. Unless you know absolutely for sure that neutrals and grounds are not shared, you need to treat each and every wire as if it could be hot while they're dangling loose.
In practice this means don't put yourself between any two wires in the box, or between any wire and a real earth ground.