For electric circuits to work they must be:

An electric circuit is like a pathway made of wires that electrons can flow through. A battery or other power source gives the force (voltage) that makes the electrons move. When the electrons get to a device like a light bulb, your computer, or a refrigerator, they give it the power to make it work.

The word “circuit” sounds like “circle,” and a circuit needs to be circular to work. The wires have to go from the power source to the device and back again, so that the electrons can go out and come back.

Many circuits have a switch so that they can be turned on and off. When the switch is off, it makes a gap in the circuit and the electrons are not able to flow around. When the switch is turned on, it closes the gap and the electricity is able to move and make the device work.

when it gains or loses electrons

i don't understand. explain it clearly