When we squeeze a door knob, or switch on a light, we are able to do so because our nervous system has sent signals to the brain.
When we talk about our brains telling our hands to squeeze the door knob, or about the nervous system sending "signals" to the brain, or about synapses "firing," we're really talking about electricity carrying messages between point A and point B.
It is somewhat like the digital cable signal, carrying the 1s and 0s, that delivers the program "Damages."
In our bodies, though, the electrons do not flow along a wire. Instead, an electrical charge jumps from cell to cell, until it reaches where it needs to go.